7 Windows Files and Folders You Should Never Delete or Modify

This article was published in 2020 and updated in October 2026.

Messing with Windows system files can be disastrous. Delete or change the wrong one and you may not be able to log in again, or Windows may fail to start the next time you turn on your PC. In the worst case, crashes can corrupt the system drive and make your data hard to reach. Here are the seven most important Windows files and folders you should never delete or modify — and what to do instead when they take up too much space. Everything below applies to Windows 10 and Windows 11.

1. The Windows folder

The Windows folder (C:\Windows) holds the operating system itself. Deleting, moving or modifying files in it can make Windows unstable or stop it from starting, and you may have to repair or reinstall Windows to get your PC working again.

2. System32

C:\Windows\System32 contains the core Windows system files and built-in programs. It includes the DLL (Dynamic Link Library) files that Windows and many third-party applications share, the registry hives (in System32\config) and the drivers folder that lets Windows talk to your hardware. Deleting System32 or files inside it can leave Windows unable to boot. (Old internet “jokes” telling people to delete System32 to speed up their PC are exactly that — jokes with very real consequences.)

3. WinSxS

WinSxS (“Windows Side-by-Side”, C:\Windows\WinSxS) stores different versions of system components and DLL files. It is used to install updates, repair Windows and roll back changes, so it is normal for it to grow to several gigabytes — and File Explorer overstates its real size, because many of its files are shared with other folders.

Never delete WinSxS or files inside it: Windows may stop booting or fail to install updates. To shrink it safely, run Disk Cleanup and choose Clean up system files → Windows Update Cleanup, or run DISM /Online /Cleanup-Image /StartComponentCleanup in an administrator terminal.

4. Program Files and Program Files (x86)

C:\Program Files and C:\Program Files (x86) are the default install locations for 64-bit and 32-bit applications. Deleting a program’s folder directly leaves registry entries, services and shortcuts behind and can make other apps crash. To remove software, use Settings → Apps → Installed apps (or Control Panel → Programs and Features) instead.

5. System Volume Information

This hidden, protected folder exists at the root of C: and of other drives, including many USB drives. It holds important system data such as System Restore points and indexing information, and it can grow over time. Don’t try to delete it. If it uses too much space, reduce the disk space allowed for System Protection: search for Create a restore point, select the drive and click Configure.

6. pagefile.sys

pagefile.sys in the root of C: is the paging file — Windows’ virtual memory, used when physical RAM runs low. Windows locks it while running, and turning it off can cause programs to crash or the system to freeze when memory gets tight. If its size is a problem, let Windows manage it or adjust it under System → Advanced system settings → Performance → Settings → Advanced → Virtual memory.

7. swapfile.sys

swapfile.sys is a small companion to the paging file that Windows uses for apps from the Microsoft Store. It is usually only a few hundred megabytes, so removing it saves little space and can hurt performance. It is managed together with the paging file — disabling pagefile.sys also removes swapfile.sys.

What about hiberfil.sys and Windows.old?

Two large files and folders can be removed — just not by deleting them by hand:

hiberfil.sys stores the contents of memory for hibernation and Fast Startup. If you don’t need either, run powercfg /hibernate off as administrator and Windows removes the file itself.
Windows.old holds your previous Windows installation after a major upgrade. Once you’re sure you don’t want to go back, remove it via Settings → System → Storage → Temporary files → Previous Windows installation(s) or Disk Cleanup.

What if you accidentally delete a critical file or folder?

Accidental deletion is more common than virus or malware damage. If it happens, stop using the affected drive and check the Recycle Bin first. If the files aren’t there, restore them from a backup.

If Windows still starts, run sfc /scannow and DISM /Online /Cleanup-Image /RestoreHealth in an administrator terminal to repair damaged system files.
If it doesn’t start, use the recovery options (Startup Repair, System Restore or Reset this PC while keeping your files).
For personal files without a backup, data recovery software such as Stellar Data Recovery Premium or Recuva can often bring them back.

Do check: Forgot Windows 10 Password – How to Recover?

Also read: Top 8 Powerful Tools for Finding Duplicate Images in Windows PC

Conclusion

The Windows, System32 and WinSxS folders, Program Files, System Volume Information, pagefile.sys and swapfile.sys are essential parts of Windows. Deleting or modifying them can cause crashes, boot failures and data loss. If disk space is the problem, use Windows’ own tools — Disk Cleanup, Storage Sense and the settings described above — instead of deleting files by hand.

If you have accidentally deleted a critical file or folder in Windows or on external storage, check the Recycle Bin and your backups first, then try a data recovery tool. And to avoid data loss, always keep a regular backup.