A full C drive is one of the most common reasons a Windows PC slows down, refuses an update, or starts throwing save errors. The good news is that you can almost always increase C drive space without buying anything.
The eleven steps below are ordered from safest to most involved. Work down the list and stop when you have the room you need — most people never get past the first four.
To increase C drive space, start with Settings > System > Storage > Temporary files and remove what Windows offers, then delete any previous Windows installation, uninstall apps you no longer use, and trim System Restore. Together those four steps usually free the most space, and none of them touch your personal files.
Why Your C Drive Keeps Filling Up
The C drive holds Windows itself, your installed programs, and by default your Documents, Downloads, Desktop and Pictures folders. It also quietly stores a lot you never asked for.
- Windows Update keeps downloaded installers and a rollback copy of the previous version.
- System Restore reserves a slice of the drive for restore points.
- Hibernation reserves a file roughly the size of your installed RAM.
- Browsers, video editors and games build up caches that nothing ever clears.
- Cloud folders sync a full local copy of everything unless you tell them otherwise.
That is why a drive can lose tens of gigabytes without you installing a single new thing. Understanding which of these applies to your PC is what makes the difference between guessing and actually fixing it.
It also explains why the same advice does not work for everyone. A machine that has been through three feature updates has a very different problem from one with a 200 GB photo library sitting in Documents, and the steps that help each are in different sections below.
First, See Where the Space Actually Went
Do not start deleting until you know what is large. Windows has a built-in breakdown that takes ten seconds to open.
- Press
Windows + Ito open Settings. - Go to System, then Storage.
- Wait for the bar to finish calculating, then read the categories underneath — Apps, Temporary files, Documents, and so on.
- Click any category to see what is inside it.
This single screen usually answers the question. If Temporary files is enormous, step 1 will fix it. If Apps dominates, step 4 is your answer. If Documents or Pictures is the biggest slice, you need steps 8 to 10 instead.
Steps 1 to 4: The Safest Ways to Increase C Drive Space
Step 1: Clear Temporary Files
On the Storage page, click Temporary files. Windows lists caches, update leftovers, thumbnails and the Recycle Bin with a size beside each one.
Tick what you want gone and click Remove files. Read the list before confirming, because Downloads is sometimes pre-selected and that folder may hold things you still want. Microsoft covers the same categories in its guide to freeing up drive space in Windows.
Step 2: Empty the Recycle Bin and Check Downloads
Deleted files sit in the Recycle Bin taking up full size until you empty it. Right-click the bin and choose Empty Recycle Bin.
Then open your Downloads folder and sort by size. Old installers, ISO files and video downloads collect there for years and are almost always safe to remove once you have used them.
Step 3: Remove the Previous Windows Installation
After a feature update, Windows keeps your old installation in a folder called Windows.old so you can roll back. It is often one of the largest single items on the drive.
Windows deletes it automatically ten days after the upgrade, but you can clear it sooner from the same Temporary files screen. Our full guide to deleting the previous version of Windows walks through it, including what you give up by removing it early.
Step 4: Uninstall Programs You No Longer Use
Go to Settings, then Apps, then Installed apps, and sort by size.
Games, creative software and old office suites are usually the big ones. Uninstall what you genuinely do not use — but leave anything with a manufacturer name you do not recognise, since some of it is driver support your hardware needs.
Turn on Storage Sense while you are in Settings and this maintenance mostly runs itself. Microsoft explains the options in its guide to managing drive space with Storage Sense.
Windows File Management: 13 Tips to Organise Your Workspace — A tidy folder structure keeps the drive from refilling three months later.
Steps 5 to 7: Reclaim What Windows Reserves
These three steps recover space that Windows sets aside for its own features. They are safe when done in moderation, and genuinely risky when taken to extremes — the warnings matter here.
Step 5: Trim System Restore Instead of Disabling It
System Restore reserves a percentage of the drive for restore points, and on a large drive that can be many gigabytes.
Press Windows + R, type sysdm.cpl, press Enter, and open the System Protection tab. Select the C drive, click Configure, and drag Max Usage down to something modest.
Lowering the limit deletes the oldest restore points and keeps the newest, which is exactly what you want.
Do not turn System Protection off altogether, however tempting the space is. Restore points are the cheapest way back from a bad driver or a failed update, and without them your only recovery route is a reinstall. Reduce the limit, keep the feature.
Step 6: Turn Off Hibernation If You Do Not Use It
Windows reserves a hidden file called hiberfil.sys at the root of the C drive. Microsoft notes it is approximately equal to how much RAM is installed, so on a 16 GB machine that is roughly 16 GB sitting idle.
Open Command Prompt as administrator and run the command below, then restart. Microsoft documents the procedure in how to disable and re-enable hibernation.
powercfg.exe /hibernate offTo bring it back later, run powercfg.exe /hibernate on from the same elevated prompt.
This only makes sense on a desktop you always shut down properly. On a laptop, hibernation is what preserves your open work when the battery runs out, and turning it off also disables hybrid sleep and the fast startup behaviour that depends on the same file.
Step 7: Let Windows Manage the Page File
The page file is virtual memory Windows uses when RAM runs short. It is usually a few gigabytes.
Press Windows + R, run sysdm.cpl, open Advanced, click Settings under Performance, open Advanced again, then Change under Virtual memory. If it is set to a large fixed size, switching it back to Automatically manage paging file size for all drives often recovers a little room.
Do not shrink the page file to a token size or disable it to chase a few gigabytes. When memory runs short, Windows will close programs or crash instead of paging, and you can lose unsaved work. This is the smallest win on the list and the easiest one to get wrong.
Steps 8 to 10: Move Data Off the C Drive
If your personal files are the problem rather than Windows, cleaning system folders will never be enough. Move the data instead.
Step 8: Relocate Your User Folders
Documents, Downloads, Pictures, Music and Videos can each live on another drive without breaking anything.
Right-click the folder, choose Properties, open the Location tab, click Move, and pick a folder on the other drive. Windows updates every shortcut and app that points at it.
Do them one at a time and let each move finish before starting the next.
Step 9: Turn On Files On-Demand in Your Cloud Folder
OneDrive, Dropbox and Google Drive keep full local copies by default, so a large cloud account fills the C drive twice over.
In OneDrive, right-click the cloud icon, open Settings, and enable Files On-Demand. Files then show as placeholders and download only when you open them. The equivalent setting in other services is usually called selective sync or streaming.
Step 10: Install Large Apps and Games Elsewhere
Steam, Epic, Xbox and most creative suites let you choose an install location, and Steam can move an installed game between drives without redownloading it.
Point new installations at a second drive and the C drive stops losing ground every time you install something.
Windows Data Recovery: How to Recover Lost Files — Read this before moving anything large, so a half-finished move is not a disaster.
Step 11: Add or Upgrade the Drive
If you have worked through the list and the drive is still tight, the honest answer is that it is too small for how you use the PC. No amount of cleanup fixes a 128 GB drive in 2026.
- A desktop usually has a spare slot, so adding a second SSD is often the cheapest fix.
- A laptop may have one M.2 slot and no room for a second, in which case you replace the existing drive and clone it across.
- Extending the C partition into free space on the same physical disk is possible in Disk Management, but only if the unallocated space sits directly after the C partition.
Whatever route you take, back up before you start. Cloning and repartitioning both put every file on the drive at risk if something is interrupted.
What Not to Do
Plenty of advice on this topic will cost you more than it saves. Skip all of the following.
- Do not compress the C drive. The Compress this drive option trades processor time for space on the drive Windows runs from, and the slowdown is more noticeable than the space is useful.
- Do not delete files from Windows or System32. Nothing in there is safe to remove by hand, whatever a forum post claims.
- Do not use registry cleaners to free space. The registry is a few megabytes. They cannot give you meaningful room and can break a working system.
- Do not disable System Restore or the page file entirely. Both are covered above — reduce them, do not remove them.
- Do not delete the Windows Installer folder. It looks like leftover junk and is actually what lets you repair or uninstall your installed programs.
How to Stop It Filling Up Again
Freeing space once is easy. Keeping it free is a matter of three habits.
- Leave Storage Sense on so temporary files and the Recycle Bin clear themselves on a schedule.
- Keep roughly ten to fifteen percent of the drive free. Windows needs working room for updates and virtual memory, and a drive filled to the brim is a common cause of sluggishness.
- Check the Storage page once a month. Catching a runaway cache early takes a minute; discovering it when an update fails takes an afternoon.
Done once properly, this list should not need repeating for a long time. Most people who have to increase C drive space twice in a year are hitting the same cause each time — usually a cloud folder syncing everything locally, or a games library installed on the wrong drive — and fixing that once beats cleaning up every few months.
If the PC still feels slow after the drive has room, the drive was probably not the whole story — work through a proper slow computer checklist, and if the disk sits pinned at full load, our guide to 100% disk usage in Windows covers that separately.
Frequently Asked Questions
How much free space should the C drive have?
Aim for at least ten to fifteen percent of the total size. Windows needs headroom for updates, temporary files and virtual memory, and performance suffers once a drive is nearly full.
Is it safe to delete temporary files?
Yes. The items Windows lists under Temporary files are caches and leftovers it can rebuild. The only entry to check carefully is Downloads, which holds real files you may still want.
Will increasing C drive space make my PC faster?
Sometimes. A drive with almost no free space slows down because Windows has nowhere to work, so clearing it helps. If the drive already had room, the slowness has another cause.
Can I extend the C drive from another partition?
Only if the free space is unallocated and sits immediately after the C partition on the same physical disk. Disk Management will grey out Extend Volume otherwise.
What is taking up so much space if my files are small?
Usually a previous Windows installation, restore points, the hibernation file, or a cloud folder syncing everything locally. The Storage page shows which of those applies to your PC.
Is it safe to delete the Windows.old folder?
Yes, once you have confirmed the current version of Windows works properly and your files are all present. You lose the option to roll back to the previous version.
