Fix Low Disk Space After Windows 10 Upgrade

If your PC shows a low disk space warning right after upgrading to Windows 10, the usual culprits are leftover files from the previous installation, the Windows.old folder, and temporary upgrade files. You can often reclaim 10–30 GB by running Disk Cleanup, deleting the Windows.old folder, and clearing the SoftwareDistribution download cache.

Why Upgrades Eat Disk Space

Windows 10 upgrades are designed to be reversible. To let you roll back if something goes wrong, the installer keeps a full copy of your old system in a hidden folder called Windows.old. That folder can be 10–20 GB or more, depending on how large your previous Windows installation was. On top of that, the upgrade process downloads a large set of installation files (often several gigabytes) and stores them in the C:\Windows\SoftwareDistribution\Download folder. After the upgrade completes, those files are no longer needed, but Windows doesn’t always delete them automatically.

Another common space consumer is the hibernation file (C:\hiberfil.sys), which can be 40–75% of your RAM size. If you never use Hibernate, disabling it can free several gigabytes. Finally, the page file (C:\pagefile.sys) and swapfile.sys are managed by Windows and usually shouldn’t be touched unless you’re comfortable with advanced settings.

Quick Fix: Run Disk Cleanup

The fastest way to clear upgrade leftovers is the built-in Disk Cleanup tool. Here’s how:

Type Disk Cleanup in the Start menu and open the app.
Select the drive where Windows is installed (usually C:) and click OK.
Click Clean up system files. This re-scans the drive with administrator privileges.
Check the boxes for Previous Windows installation(s), Temporary Windows installation files, and Temporary files.
Click OK and confirm deletion.

If you don’t see “Previous Windows installation(s)� in the list, it means the Windows.old folder has already been removed (Windows deletes it automatically after 10 days) or the cleanup tool didn’t detect it. In that case, proceed to the manual removal method below.

Delete Windows.old Manually

If Disk Cleanup doesn’t remove the folder, you can delete it manually using Storage Sense or Command Prompt. The manual method is more thorough and also clears the $Windows.~WS and $Windows.~BT folders if they exist.

Open Settings → System → Storage.
Click Temporary files. Wait for the scan to finish.
Check Previous version of Windows and any other items you want to remove.
Click Remove files.

Alternatively, use Command Prompt as an administrator:

Right-click the Start button and select Command Prompt (Admin) or Windows PowerShell (Admin).
Type rd /s /q C:\Windows.old and press Enter.
If you see a “file in use� error, reboot and try again.

After deletion, you lose the ability to roll back to your previous Windows version. Only do this if you’re sure the new installation is working correctly.

Clear the SoftwareDistribution Cache

The upgrade files downloaded by Windows Update are stored in C:\Windows\SoftwareDistribution\Download. These are not needed after the upgrade. To clear them safely:

Open Command Prompt as administrator.
Type net stop wuauserv and press Enter. This stops the Windows Update service.
Type net stop bits and press Enter. This stops the Background Intelligent Transfer Service.
Open File Explorer and navigate to C:\Windows\SoftwareDistribution\Download.
Select all files inside and delete them. If some are in use, skip them and reboot.
Go back to Command Prompt and type net start wuauserv and net start bits to restart the services.

This does not affect your installed updates—it only removes cached installation files. Windows will re-download them if needed for a future update.

Disable Hibernation to Free RAM-Sized Space

The hibernation file reserves disk space equal to about 40–75% of your installed RAM. If you never use the Hibernate power option, you can disable it and reclaim that space.

Open Command Prompt as administrator.
Type powercfg /h off and press Enter.

This immediately deletes hiberfil.sys. To re-enable hibernation later, type powercfg /h on. Note that this also disables Fast Startup, which uses the hibernation file to speed up boot times. If you rely on Fast Startup, weigh the trade-off: you lose a few seconds of boot time but gain several gigabytes.

Other Space Hogs After Upgrade

Beyond the upgrade leftovers, a fresh Windows 10 installation can accumulate other large files. Check these areas:

WinSxS folder (C:\Windows\WinSxS) – This is the component store. It can grow large, but you should not delete it manually. Use the Disk Cleanup option “Windows Update Cleanup� to safely reduce its size.
Delivery Optimization Files – Windows Update may cache updates for other PCs on your network. Clear them via Settings → Update & Security → Delivery Optimization → Advanced options → Delete cached files.
Recycle Bin – Empty it if it’s full.
System Restore Points – These can consume several gigabytes. Go to Control Panel → System → System Protection → Configure to adjust the max usage or delete all but the latest restore point.

When to Use a Third-Party Tool

If you’ve done all the above and still have low disk space, you might want to use a disk space analyzer like WinDirStat or TreeSize Free. These tools show you exactly which folders and files are taking up space. They are read-only by default, so they won’t delete anything unless you tell them to. This is useful for finding large media files, old downloads, or app caches that you forgot about.

Be cautious with any tool that claims to “clean� your system automatically. Stick to well-known utilities and always create a system restore point before making major changes.

Frequently Asked Questions

How long does Windows keep Windows.old?

Windows automatically deletes the Windows.old folder after 10 days. However, if you run Disk Cleanup and select “Previous Windows installation(s),� it removes it immediately. The 10-day timer resets after each feature update, so if you upgraded recently, you may have more than one Windows.old folder (in rare cases).

Is it safe to delete Windows.old?

Yes, as long as your new Windows 10 installation is stable and you don’t plan to roll back to the previous version. Deleting it only removes the backup files needed for uninstalling the upgrade. It does not affect your current system or personal files.

Why is my disk still full after deleting Windows.old?

There could be other large files like the hibernation file, page file, or WinSxS folder. Also, check if you have any large applications or media files. Use a disk space analyzer to see the breakdown. Sometimes the “System Reserved� partition is full, but that’s a separate issue that doesn’t affect your main drive’s free space.

Can I move Windows.old to another drive?

No, Windows.old must stay on the same drive as the current Windows installation for the rollback feature to work. If you move it, Windows won’t recognize it. If you need the space, just delete it.

Will deleting SoftwareDistribution break Windows Update?

No. The Download folder only contains cached update files. Stopping the Windows Update service, deleting the contents, and restarting the service is a standard troubleshooting step. Windows will re-download any needed files on the next update check.

How much space should I have free after a clean install of Windows 10?

A 64-bit installation of Windows 10 typically uses about 20–25 GB for the system files, plus additional space for the page file, hibernation file, and restore points. A 32-bit install uses slightly less. For comfortable operation, Microsoft recommends at least 32 GB of storage, but 64 GB or more is better if you install many programs.

General steps for current mainstream versions; menus can differ by device and version. See the disclaimer or report an error.

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