Many people report that the Disk Cleanup tool hangs and the following message is displayed:

Disk Cleanup is calculating how much space you will be able to free on (C:). This may take a few minutes to complete. Scanning: Compressed old files.

According to this knowledge base article, this occurs because of a problem with the Windows registry. You can resolve the problem by deleting the incorrect registry key using the steps listed below. Since you are making a change to the registry, you should create a backup of the registry key first in the event you run into problems after.

1. Click Start and click Run.

2. Type regedit.exe and click OK.
3. Within the Registry Editor, locate the following registry key: HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\Explorer\VolumeCaches.
4. Under Volumes Caches, select the Compress old files registry key as shown in the figure.
5. From the Edit menu, click Delete.
6. Close the Registry Editor.