I run the Disk Cleanup tool, click on the "Clean up system files" button, after which it shows there is 4.55 GB of "Windows Update Cleanup" that can be removed. I click "OK" and then click "Delete Files", after which the progress bar moves along slowly but surely, and then the cleanup app closes. I check my disk space... and nothing has changed... I've tried this four times the last few weeks and it has not worked. Any idea what could be keeping the cleanup from working? I really need the space now.