For years now, i’ve occasionally had a Windows XP box that would mysteriously fill up its HDD over night. Sometimes loosing as much as 10GB in one evening.

Several years ago I researched the problem after tracking the missing space down to the c:\windows\csc folder. Originally my google searches and lookups on Microsoft’s knowledge bases led me to believe that this folder was where Windows Restore kept its data.

That may or may not be true.

What is stored in the folder, and is the actual cause of the problem we have been having, is the cache for any File Sync Operations.

To reclaim the space:

1 open Windows Explorer

2 Tools -> Folder Options

3 “Offline Files” Tab

4 Uncheck “Enable Offline Files” and reboot the computer.

5 Delete everything in c:\Windows\csc (but not the directory itself). It should let you delete all but 1 or 2 files.

There is an option there to limit the amount of space that the cache should use, but it doesn’t seem to work. 10GB is considerably more than the 10% (of a 20GB drive) that we had it set to.