How do you know it's full (or not full)?
Did you right-click properties on the drive and saw that the bytes free wasn't zero?
IIRC, windows starts complaining about low disk space when you get to say 95% full / 50MB free kind of area to warn you that things are getting tight. This is far better than the 100% used fatal error and you're in a hurry to save your precious word document.
When did you last do any normal disk housekeeping, say...
- Empty the trash can.
- Empty all the temp directories.
- Run internet explorer, options, clear disk cache, and choose a more appropriate setting.
- Ditto for any other browser you may have.
- Ditto for other programs like Adobe acrobat and some image viewers which also has disk caches.
- backup and defragment the drive.
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