After a major Windows update or upgrade, Windows automatically keeps a backup copy of your previous installation in a folder called Windows.old, along with some related system folders. This safety net lets you roll back if something goes wrong, but it can take up anywhere from 15GB to over 30GB of space, and it isn't needed forever.
Key takeaway: Windows.old is only needed for the first 10 days after an update as a rollback safety net; once you're confident everything is working properly, it's safe to remove through Disk Cleanup.
Before you start: Don't delete Windows.old if you've noticed any problems since your last Windows update, or if it's been less than 10 days — you may still want the option to roll back.
Checking if you can still roll back
- Go to Settings > System > Recovery.
- Look for a "Go back" or "Previous version of Windows" option — if it's present and not greyed out, your Windows.old folder is still available as a safety net.
- If this option has already disappeared, Windows has automatically removed Windows.old itself after the standard 10-day window.
Removing Windows.old via Disk Cleanup
- Click Start, type "Disk Cleanup," and open it.
- Select your main drive (usually C:).
- Click "Clean up system files" to unlock the full list of categories.
- Tick "Previous Windows installation(s)" along with "Temporary Windows installation files" if shown.
- Click OK, then confirm by clicking Delete Files.
This process can take several minutes, since it's removing a genuinely large amount of data. Don't interrupt it or shut down your PC while it's running.
What if Windows.old doesn't appear in Disk Cleanup?
If it's already past 10 days since your update, Windows will have automatically deleted it for you, so there's nothing left to clean. You can confirm this by checking Settings > System > Storage and looking at the "Temporary files" category, which will no longer list a previous Windows installation.
Tip: If you're confident everything is working well after an update, there's no benefit to keeping Windows.old around longer than necessary — reclaiming that space is generally the better trade-off for most users.
Other related folders worth checking at the same time
While you're clearing out Windows.old, it's worth checking Disk Cleanup's full list for a few related categories that often appear alongside it. "Windows Update Cleanup" removes redundant copies of update files that Windows keeps temporarily to support uninstalling a recent update; once you're confident an update hasn't caused problems, these are safe to clear too. "Delivery Optimisation Files" holds pieces of update files Windows may have used to help share updates with other PCs on your network, and can also be safely cleared. Finally, "Temporary Windows installation files" specifically relates to leftover files from the setup process itself, distinct from the main Windows.old folder, and is generally safe to include in the same clean-up pass.
Clearing all of these together in one Disk Cleanup session, rather than just Windows.old alone, tends to produce a noticeably larger amount of freed space than tackling Windows.old in isolation.
Frequently asked questions
- How long does Windows keep the Windows.old folder?
- By default, Windows automatically deletes it after 10 days, though you can remove it manually sooner via Disk Cleanup if you're confident you won't need to roll back.
- Can I delete Windows.old by just going into the folder and deleting files?
- It's not recommended. The folder contains protected system files with special permissions, so manually deleting inside it often fails or causes errors — Disk Cleanup is the safe, intended method.
- Will deleting Windows.old affect my current Windows installation?
- No, it only removes the backup copy of your previous installation. Your current, running version of Windows and all your files remain completely unaffected.