A nearly full C: drive is more than a cosmetic warning. Microsoft says low storage can affect performance and make it difficult to install Windows updates. [R1][R2]
The safest way to recover space is not to hunt for the biggest-looking system file and delete it. Start with storage that Windows already knows how to clean.
Start with Windows' own cleanup tools
Open Settings → System → Storage → Cleanup recommendations.
Windows can identify categories such as:
- temporary files;
- large or unused files;
- files synced to cloud storage;
- apps you rarely use. [R1]
Review the suggestions before deleting anything. A file being listed as large does not mean you no longer need it.
Storage Sense can also remove unnecessary temporary files and old items from the Recycle Bin automatically. By default, it does not clean the Downloads folder or cloud content unless you configure it to do so. [R2]
That makes Storage Sense much safer than treating every large folder as disposable.
Personal files are often the easiest space to recover
Videos, downloads, installation files, photos, virtual-machine images, and other personal files can consume far more space than Windows itself.
Microsoft recommends checking your personal folders for large files and either deleting files you no longer need or moving files you want to keep to another drive or external storage. [R1]
Before deleting a large personal file, make sure it is either genuinely unnecessary or backed up somewhere else.
Uninstalling apps and games you no longer use can also recover substantial space.
Be careful with Windows.old
After a major Windows upgrade, the previous installation may be kept in Windows.old for a limited time.
Windows can offer this folder through its cleanup tools. Removing it can free significant space, but there is a cost: Microsoft warns that deleting the previous Windows installation removes your ability to return to that previous version of Windows. [R3]
If you recently upgraded and might need to roll back, keep it until you are confident the new installation works correctly.
Do not manually delete WinSxS
The WinSxS folder contains Windows components used for servicing the operating system.
It can look extremely large, but Microsoft explicitly warns against deleting files from this folder manually because doing so can damage Windows, prevent the PC from booting, or make updating impossible. [R4]
Windows has supported cleanup mechanisms for reducing the component store safely. Use Windows cleanup tools rather than deleting its contents yourself.
pagefile.sys is not ordinary junk
pagefile.sys is a Windows page file — hidden system storage used as part of virtual memory. It can also be needed for system crash dumps. Windows normally manages page-file size according to memory demand and other system requirements. [R5]
Do not delete or disable it simply because a disk-usage tool shows that it is large. Reducing virtual-memory capacity can cause applications or Windows to run out of committed memory under heavy load. [R5]
hiberfil.sys has a purpose too
hiberfil.sys is used to store memory state for hibernation and related power features. Microsoft notes that if this file is not present, the computer cannot hibernate. [R6]
Disabling hibernation can remove the file, but that is a feature trade-off, not ordinary cleanup. Do it only if you intentionally do not need hibernation.
What should I remove first?
A sensible order is:
- Windows Cleanup recommendations and temporary files.
- Recycle Bin contents you no longer need.
- Personal files you can delete or move elsewhere.
- Apps and games you no longer use.
- Previous Windows installation files only if you accept losing the rollback option.
Leave Windows-managed system files and folders alone unless Windows provides a supported cleanup method for them.
After cleanup, check This PC again and confirm that usable free space has actually increased. If the drive immediately fills again, the next step is not more aggressive deletion — it is finding out what is creating the new data.