Sudden increase in c:\windows size in win8

Suddenly, the c:\windows directory increased to 403gb. Now windows reports no space left on the disk.
Nothing was added, nor does any sub-directory within it read strangely. I have forced a full chkdsk /r, etc....
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JohnBusiness Consultant (Owner)Commented:
That is unreal and not correct. Get Tree Size Pro (Jam Software), download it, install it and run it. It will tell you where the space has gone. Backups do not (that I have ever seen) go in Windows.

Have you tried MANY unsuccessful Windows 10 upgrades. These would leave Windows.old folders. Still, it would take a lot of upgrades to get to 400 GB.

Something has gone wrong.
JohnBusiness Consultant (Owner)Commented:
Go to Admin Tools (Windows Explorer) and find Disk Cleanup. Run Disk Cleanup. When it first comes up ready, click on the Clean up System Files  button. This will cause it to search again. When it is ready, review the items for cleanup and cleanup any Windows.old folders. I am assuming you are at Windows 8 and have not yet upgraded (you can't if there is no space).
Christopher Jay WolffWiggle My Legs, OwnerCommented:
Please backup any valuable data.

Please check the size of your panther folder.  The link here says it can easily grow to many GBs.  Although the link is a bit old the theory probably still holds.  My Windows 8.1 has a panther folder.

You may already have done this, but in case it helps this link reviews repairing cross-linked files with chkdsk.

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