How to Back Up a Windows PC Properly: The 3-2-1 Rule in Practice

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On 2nd November 2026

At 12:39 am

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Short answer: A practical way to back up a Windows PC is the 3-2-1 rule. Keep three copies of your important files, put the backups on two kinds of storage, and keep one copy off site. That means the files on the computer, a second copy on an external drive made with tools already in Windows, and a third copy in the cloud. Once a month, restore a test file from each backup so you know the copies are real.

People usually search for how to back up a Windows PC when it will not start, a folder has gone, or the screen says files are locked. The copy you use every day is then the copy you cannot open. The National Cyber Security Centre advises you to back up your most important data and to keep that backup separate from the computer, so loss, theft or damage does not remove the only copy.

This plan is for a home or small office. It uses File History, one external drive and one cloud copy, plus a system image if Backup and Restore (Windows 7) is still on your PC. You can set it up in an afternoon. After that, the work is a backup day you keep and a short restore test each month.

What the 3-2-1 rule means on a home PC

The 3-2-1 rule is a memory aid. It is not a switch inside Windows.

3 copies of anything you would hate to lose. The files you open on the PC are the working copy, and that copy is not a backup. The other two are the backups.
2 kinds of storage for those backups. An external drive can be lost, dropped or left plugged in during a malware incident. A cloud account can be full, locked or closed. They fail in different ways. Two folders on the same internal disk do not count: if that disk dies, both folders go with it.
1 copy off site, so it is not in the same room as the PC. In this plan that is the cloud copy. A fire, flood or burglary can take the computer and a nearby drive together.

A USB stick that lives in the laptop bag is better than nothing, but it is easy to lose and it is not off site. Windows will not build this layout for you. You set up the two backups, then you check that a file can come back.

What to back up, and what you can leave

Back up what you could not download again or rewrite from memory: documents and PDFs, photos and home videos with no other copy, the Desktop, files you paid for that you may not be able to download twice, and any email a desktop program stores on the PC. Webmail already sits with the provider. Also keep a note of the apps you would reinstall and where each licence lives, such as a Microsoft account or an email receipt. Reinstalling Windows is the quicker half. Finding licences from memory is not.

Leave out Windows itself, programs you can download again, the Recycle Bin, and large game installs if the saves are in Documents or on the game account. If you are unsure where saves live, copy them into Documents before you rely on that.

Size the drive from your own PC. Open Settings, then System, then Storage, and look at Documents, Desktop and Pictures. The external drive needs more free space than those folders, with room for older versions. A system image needs a further block of space, in the region of the used size of C:. Portable drives sold for home backups often start around 1 TB and go up from there, but sizes and prices change, so match the drive to your Storage page and leave spare room.

On a shared PC, another person’s Windows sign-in is not included in yours. Back up each account that holds real files, or keep shared work in a folder your backup includes. If the PC stores information about customers or anyone other than you, a missing copy affects them too. Ask a qualified adviser if you are unsure of your duties. This is a backup method, not legal advice.

Where the three copies live

Use three places, and write down anything you chose to leave out.

Copy	Where it lives	What it is for
Working files	The PC’s internal drive	Daily work. If this disk fails, this copy is gone.
External drive	A separate USB drive, NTFS, unplugged after each backup	File versions through File History, plus a system image if it fits.
Cloud	An account that still has free space	The off-site copy, with its own sign-in checks.

You do not need a second computer. You need a drive you will not borrow for odd jobs, and enough cloud space for what you called essential. If the free cloud allowance is smaller than your photos, sync Documents and the newest photos first, keep the older archive on the external drive, and write that split down. A full cloud account stops taking new files. Check the space figure in the cloud settings after the first upload.

Set up File History on an external drive

Give the external drive one job: backups. A drive that also carries random downloads gets filled or formatted. Plug it into a USB port on the PC rather than an unpowered hub.

Check the drive format

File History needs NTFS. In File Explorer, right-click the drive, open Properties, and read the file system. If it already says NTFS, do not format it. If the drive is new or empty and shows exFAT or FAT32, right-click it, choose Format, pick NTFS, set a name you will recognise such as PC-BACKUP, and run a quick format. Formatting erases that drive. Stop if it still holds the only copy of anything you need.

Turn File History on

Open Start, type File History, and open it. Windows 11 still offers this through Control Panel. On Windows 10 you can also use Settings, then Update & Security, then Backup. Menu names vary a little, so search if a label does not match.
Select the external drive and turn File History on.
Open Exclude folders and skip large items you can replace, such as a downloads folder full of installers.
Open Advanced settings. Hourly is a sensible default while the drive is plugged in. If space is tight, keep saved versions until space is needed. If the drive has plenty of room, a year, or forever, keeps older copies for longer. You can change this later.
Choose Back up now. Leave the PC awake and on mains power. The first run copies everything, so a large photo library can take hours. Later runs copy changes. Wait until the page shows a time for the last backup. If it shows an error, read it before you unplug. A drive that fell asleep, or a folder Windows could not read, is a common cause.

Include a folder File History skips

File History covers your libraries and the usual profile folders: Desktop, Documents, Pictures, Music and Videos. A folder such as D:\Work is ignored until you add it. Right-click that folder, choose Include in library, and pick Documents. On Windows 11 you may need Show more options before Include in library appears. Run the backup again, open Restore personal files, and confirm the folder is listed.

Eject the drive in File Explorer and unplug it. Keep it out of the bag you travel with. A drive that stays connected all day is convenient, and it is also visible to malware that can write to your other drives.

Add a system image and a recovery USB

File History brings files back. It does not reinstall Windows or your programs. For a snapshot of the same PC, search the Start menu for Backup and Restore (Windows 7). On current Windows 10 and Windows 11 that legacy tool is still the built-in way to create a system image. If search finds nothing, skip the image. File History and the cloud copy still cover your files.

Choose Create a system image, select the external drive, and include C: plus any other drive that holds programs or files you want in the snapshot. You need free space in the region of the used size of those drives. If the backup drive cannot hold both an image and File History, keep File History. Single-file restore is what you will use in a normal month.

Make a recovery USB on a spare stick of 16 GB or more. Search for Create a recovery drive. The wizard erases that stick. Copying system files onto it is useful when the stick has room. Label the stick and keep it with the backup drive, not plugged in day to day.

Take an image when the PC is set up the way you like, and another before a repair or a large change. An image restores that same computer. It is a poor way to move a setup onto a different model, and it can fail when the hardware does not match. On a new PC, restore files from File History or the cloud, then reinstall apps from your list.

Do not start System Image Recovery to see what the screens look like. Restoring an image overwrites the drives you included.

Keep the off-site copy in the cloud

The third copy should not sit in the same building as the PC. OneDrive is built into Windows 10 and Windows 11. Another cloud storage service you already use can do the same job if the account has room. You do not need a second service on top.

For OneDrive, open the cloud icon in the taskbar and sign in. Look for Backup or Manage backup. The wording shifts between versions. Turn on Desktop, Documents and Pictures, or only the folders that actually hold your work. You can also search Settings for Windows backup. Wait until the icon shows those folders are up to date.

Sync is not a backup on its own. If you delete a file, or something encrypts it, the cloud copy can change to match. Version history and the recycle bin are the safety net, and only for as long as that service keeps them. The period is not the same on every account. After you do the test below, read the retention note in your own account rather than trusting a figure you remember.

If cloud space is smaller than your library, choose on purpose. Send documents and photos you could not replace. Leave older archives on the external drive, and write the split down. If a small office PC must open key folders with no internet, right-click those folders and choose Always keep on this device. Still keep the external copy.

Use a long, unique password on the cloud account and turn on its extra sign-in check. A third copy that opens with a reused password is a weak copy.

Keep malware away from the backup

A dead disk is only one way to lose files. If a program can change every drive it can see, a backup left plugged in as a normal drive letter can be encrypted with your documents. Unplug the external drive when File History has finished. Plug it in on a day you will remember, let the backup finish, eject it, and store it away from the laptop.

If a ransom note appears, leave the backup drive unplugged and disconnect the PC from the network. From another device, check whether the cloud copies still open as ordinary documents. Clean the PC before you restore. Putting files back onto a machine that is still infected can encrypt the new copies as well. If you are not confident doing that cleanup, a repair shop or someone qualified is a sensible next step. This article does not remove malware.

If Settings, under Privacy & security, shows Device encryption, or if search finds BitLocker, turn it on and keep the recovery key somewhere other than only on that PC. A Microsoft account often stores the key when the drive was encrypted that way. Keep a second record in a password manager or on paper stored apart from the laptop. Pro editions can encrypt the external drive as well. Many Home PCs show Device encryption only when the hardware supports it. If the setting is missing, a strong Windows sign-in and a drive kept out of sight still matter. Encryption does not replace the off-site copy.

Run a monthly test restore

A backup you have never restored is a theory. Once a month, bring one unimportant file back from the external drive and from the cloud. That is the habit that tells you the plan works while nothing important is missing.

Test the external drive

In Documents, create a folder called Restore-test.
Copy a spare document into it. Do not use the only copy of a file you need this week.
Plug in the drive, open File History, and run Back up now. Wait until it finishes.
Delete only the copy inside Restore-test.
Open Restore personal files, find that folder, select the file and restore it.
Open the file and check the contents.

If the folder is missing, File History never saw it. Fix the included folders before you trust the drive with real work. Previous Versions on the file’s Properties page is another way to see copies File History has already saved. If that tab is empty, the file was not in a backed up folder, or the drive was not connected for a run.

Test the cloud copy

Save a small text file in a folder that syncs, and wait until the cloud icon says it is up to date.
Delete that file on the PC.
Choose View online from the cloud icon, open the recycle bin, and restore the file.
Confirm it comes back to the PC, and read how long that service says it keeps deleted files.

Check the recovery USB without wiping the PC

About once a quarter, confirm the recovery USB boots, if you made one. Restart, open the boot menu, and choose the USB. The key differs by PC maker. Watch the first screen when you switch on, or check the manual. Stop when the recovery options appear, then turn the PC off. Do not choose Reset this PC. Do not choose System Image Recovery unless you intend to overwrite the drive.

Write the date, and which file you restored, on a note kept with the backup drive. If you skip a month, do the test when you remember. Skipping is not a reason to stop.

A routine you can keep

When	What to do
After the first setup	File History shows a successful time, the cloud folders are up to date, and one test restore has worked.
Backup day	Plug in the drive, run Back up now if it does not start, confirm there is no error, eject, and unplug.
Once a month	Restore test for the drive and the cloud. Check free space on both.
Before a repair, a move, or handing the PC over	Fresh backup, cloud up to date. Keep the external drive with you unless the repairer truly needs it.
When you replace the PC	Restore files from File History or the cloud. Reinstall apps from your list. Do not treat an old system image as the move plan.

Once a week is a solid rhythm for a home PC that is often asleep or shut down, with an extra run after a large batch of photos or a finished piece of work. File History can run every hour while the drive is connected, which suits a desktop that stays in one place. If you miss a week, plug the drive in when you next remember. A rhythm you keep beats a stricter one you drop.

Mistakes that leave you with no backup

Treating a sync folder as a backup, then emptying the cloud recycle bin without looking.
Leaving the only external drive plugged in all week, or in the same bag as the laptop.
Backing up the wrong Windows account on a shared family or office PC.
Formatting the backup drive later because someone needed a stick for a one-off job.
Never checking free space, so File History or the cloud upload stopped months ago.
Opening the backup folder in File Explorer and assuming a restore will work, without ever using Restore personal files.

FAQ

Is File History a full backup of the PC?

No. It keeps versions of files in the folders it covers. It does not reinstall Windows or your programs. A system image is the extra snapshot for the same PC, and only when the external drive has room for it.

Does OneDrive on its own meet the 3-2-1 rule?

No. It can be the off-site copy, which is one of the three. The files on the PC are the working copy, not a backup, and sync can spread a deletion or an encrypted file. The external drive is how you roll back without depending only on the cloud retention period.

How often should I back up a Windows PC?

While the external drive is connected, hourly File History is a sound default. If the PC is off most days, a weekly backup day is a solid minimum, plus a run after you add a lot of new files. Leave the cloud signed in so it updates as you save. Do the restore test every month even when the backups themselves are more frequent.

What if the cloud account is too small for my photos?

Put documents and irreplaceable photos in the cloud, and keep the full set on the external drive. Write down what is not off site. A smaller third copy of the files you most need is still a third copy. Check the storage reading so a full account does not stop without you noticing. Look at the allowance in your own account rather than assuming a fixed free amount.

I only see Windows Backup in Settings. Is that enough?

On Windows 11, Windows Backup is mainly your Microsoft account and OneDrive: folders, settings and a list of apps. Use it for the cloud half of this plan if that is the screen you are offered. Also search for File History and use the external drive. That Settings page is not a substitute for an unplugged drive, and it is not the system image tool.

Can I store ordinary files on the backup drive as well?

You can, and it is a common way to lose the backup. The drive fills up, or someone formats it for another job. A drive that does backups and nothing else is easier to trust. If you must share the space, label it clearly and do not reformat it.

Sources

National Cyber Security Centre, Always back up your most important data (Top tips for staying secure online).