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Question

My computer shows 90% used space on drive C.

How do I add more space?

Answer 1

Whether you can add more space or clear space, depends on the size of your drive and the partition layout.

1

Right click your Start Button and open Disk Management.

Expand the bottom pane in Disk Management so all drives and partitions are visible in that pane.

Please provide a screenshot of that window.

2

Download the free TreeSize app from the Microsoft Store.

Very Important - to run TreeSize, you must right click its icon and choose Run as Administrator.

Please provide a screenshot of your C drive in that TreeSize utility, so I can see your hard drive and work out where that space is being used and if there is an underlying problem.

Please ensure the full TreeSize window is in the screenshot, there is information on the top and bottom bars I needs to see.

Answer 2

To add more free space on drive C in Windows, use a combination of cleanup and moving data off the drive.

1. Run Disk Cleanup
   1. In the search box on the taskbar, type disk cleanup and select it.
   2. Select drive C: and choose OK.
   3. Select the check boxes for the file types to delete (for example Temporary Internet Files, Thumbnails, etc.).
   4. Select Clean up system files, choose C: again, then select additional system file types to remove (such as previous Windows installations if shown and no longer needed).
   5. Select OK > Delete files.
2. Turn on Storage Sense (Windows 10/11)
   1. Go to Start > Settings > System > Storage.
   2. Turn Storage Sense to On so Windows automatically removes temporary files and cleans the Recycle Bin.
   3. Select Storage Sense and configure how often it runs and how aggressively it cleans temporary files and Recycle Bin contents.
3. Delete or move large personal files
   1. Open File Explorer from the taskbar.
   2. Under This PC, open folders like Videos, Music, Pictures, and Downloads.
   3. Switch to Details view and sort by Size to find the largest files.
   4. Delete files that are no longer needed, then empty the Recycle Bin.
   5. For files to keep but not store on C:, connect a USB drive or SD card, select the files, and use Home > Move to > Choose location (Windows 10) or Cut and Paste to the external drive (Windows 11).
4. Use an external drive for updates (if low space blocks Windows updates) If Windows says more space is needed to install a feature update, connect an external storage device and follow the on-screen instructions. See “Get more space with external storage” in the linked documentation.
5. Optionally compress the OS drive (advanced)
   1. Open File Explorer, right‑click C: and select Properties.
   2. On the General tab, select Compress this drive to save disk space > Apply > OK. This does not delete files but may slightly affect performance on some systems. You can undo it later by clearing the same check box.

If C: remains critically full after these steps, consider moving more personal data to another internal drive (if available) or upgrading the physical disk to a larger capacity drive.

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References:

• Free up drive space in Windows
• Manage drive space with Storage Sense
• Fix low disk space errors quickly in Windows