Where the space on the C: drive goes and how to get it back

The C: drive fills up even when you don’t install anything on it. The reason is that Windows keeps several large system files and folders on it that grow on their own. Most of them can be safely reduced or removed — and you can get tens of gigabytes back without buying a new drive.

First, see what’s taking up the drive. The easiest way is Settings → System → Storage: Windows shows a breakdown by category. For a manual review of large files and programs, Files Inspector is more convenient — it clearly shows what takes up the most space.

Next — the six main space consumers and what to do about them.

1. hiberfil.sys — the hibernation file

What it is. When the computer enters hibernation, Windows saves the contents of RAM to the disk so that everything can be restored after turning it on. This data is stored in the hidden file C:\hiberfil.sys.

How much it takes. Comparable to the amount of RAM: with 8 GB of RAM it’s usually 3–8 GB, with 16 GB — up to 16 GB.

What to do. If you don’t use hibernation (most people use regular Sleep or a full shutdown), the file can be turned off:

1. Open Command Prompt as administrator: Start → type cmd → right-click → “Run as administrator”.
2. Enter the command powercfg /h off and press Enter.

The file disappears and the space is freed immediately. You can bring everything back with the command powercfg /h on.

Important: disabling hibernation also disables Windows Fast Startup. Starting the computer will become slightly slower — usually by a few seconds. If that’s not critical, feel free to turn it off.

2. pagefile.sys — the paging file

What it is. Virtual memory. When there isn’t enough RAM, Windows moves some data to the file C:\pagefile.sys. This is a normal working mechanism, not junk.

How much it takes. Usually 4 to 16 GB — Windows manages the size itself.

What to do. Most of the time — nothing. Contrary to advice on the internet, you shouldn’t completely disable the paging file: without it, some programs and games start crashing when memory runs low. The space gain is small, the risk is real.

The only reasonable option is to move the paging file to another drive if you have a second drive and the C: drive is very small (for example, a 120 GB SSD). This is done in “Advanced system settings”, in the virtual memory settings. If in doubt, just leave it as is.

3. OneDrive cache

What it is. OneDrive syncs your documents, photos, and desktop with the cloud, and keeps local copies on the C: drive. If a large amount is being synced, the OneDrive folder quietly eats up tens of gigabytes.

How much it takes. Depends on what you sync. It can be 5 or 100 GB.

What to do. Turn on “Files On-Demand” — then only the files you actually use remain on the disk, and the rest are downloaded from the cloud on click:

1. Right-click the OneDrive icon in the notification area (next to the clock).
2. Select “Settings”.
3. Turn on “Files On-Demand”.

After enabling it, you can right-click the OneDrive folder and choose “Free up space” — local copies turn into links to the cloud.

Important: the files are not deleted — they stay in the cloud and are downloaded again when opened. It’s inconvenient with slow internet, but it works great for saving space.

4. Restore points

What it is. Before installing programs and updates, Windows creates restore points — “snapshots” of the system state that you can roll back to if something goes wrong. They are stored in the hidden System Volume Information folder.

How much it takes. Windows can allocate up to 5–10% of the drive’s capacity for them. On a 500 GB drive that’s tens of gigabytes, and old points accumulate unnoticed.

What to do. Old points can be deleted, keeping the most recent one:

1. Press Win+R, type sysdm.cpl, and press Enter.
2. Go to the “System Protection” tab.
3. Select drive C: and click “Configure” → “Delete”.

Or do it through Reg Organizer — the cleanup section has removal of old restore points.

Important: don’t delete the only recent restore point. Keep at least one in case of a failure.

5. The Downloads folder

What it is. A regular folder where files from the browser are downloaded: installers, archives, documents, videos. It’s often forgotten, and over time tens of gigabytes of old installers pile up there.

How much it takes. Depends on your habits. For most users it’s one of the largest consumers.

What to do. Go through the folder and delete everything you no longer need: old program installers, duplicates, already-watched videos. Move files you’d hate to delete to another drive or an external storage device.

To quickly find the largest files, use Files Inspector — it sorts the drive’s contents by size, and you’ll immediately see what to delete first.

6. Windows.old — the previous version of Windows

What it is. After a major update (for example, upgrading to Windows 11 or installing a big update), Windows saves the previous system to the C:\Windows.old folder so you can roll back.

How much it takes. Usually 20–30 GB.

What to do. If the update went fine and you don’t plan to return to the old version, the folder can be deleted:

1. Settings → System → Storage → Temporary files.
2. Check “Previous versions of Windows” and click “Remove”.

Or use Reg Organizer — it can remove the previous version of Windows along with the installation temporary files.

Important: Windows deletes Windows.old itself about 10 days after the update. If the folder is there, the update was recent. Make sure the system is running stably before deleting it.

Short summary

The safest and fastest win is the Downloads folder, Windows.old, and hiberfil.sys: usually tens of gigabytes with no risk at all. Delete restore points while keeping the most recent one. Switch OneDrive to “Files On-Demand” mode. Don’t touch the paging file — the space saving isn’t worth the stability issues.

The easiest way to find large files and programs is with Files Inspector, and to clean the system of temporary files, old restore points, and the previous version of Windows — with Reg Organizer. Both programs show exactly what’s taking up space before you delete anything.