This is for winxp but most of the tools and file systems are the same.....
Disk Cleanup Tool Stops Responding While Compressing Old Files
IMPORTANT: This article contains information about modifying the registry. Before you modify the registry, make sure to back it up and make sure that you understand how to restore the registry if a problem occurs. For information about how to back up, restore, and edit the registry, click the following article number to view the article in the Microsoft Knowledge Base:
256986 Description of the Microsoft Windows Registry
When you try to compress old files, the Disk Cleanup tool may stop responding (hang) and you receive the following message:
Disk Cleanup is calculating how much space you will be able to free on (C:).
This may take a few minutes to complete.
Scanning: Compress old files
WARNING: If you use Registry Editor incorrectly, you may cause serious problems that may require you to reinstall your operating system. Microsoft cannot guarantee that you can solve problems that result from using Registry Editor incorrectly. Use Registry Editor at your own risk.
To work around this problem, follow these steps:
1. Click Start, and then click Run.
2. Type regedit in the Open box, and then press ENTER.
3. Locate, and then click the following registry key:
4. On the File menu, click Export, and then click Desktop, type VolumeCaches in the File name box, and then click Save.
Note This step creates a backup of the VolumeCaches registry key. If you experience any problems after you complete the steps that are listed in this procedure, you can use this backup to restore the VolumeCaches key to its original state. To restore the key, double-click the VolumeCaches.reg file on your desktop, and then click Yes.
5. Expand the following registry key:
6. Delete the Compress old files registry key.
7. Quit Registry Editor.
For additional information about the Disk Cleanup tool, click the following article number to view the article in the Microsoft Knowledge Base:
310312 Description of the Disk Cleanup Tool in Windows XP