In addition to How do I speed up Disk Cleanup or possibly prevent it from hanging?, the Disk Cleanup tool may stop responding if there are corrupted temporary files on your computer.
To workaround this problem:
01. Close all open programs, and as many Notification Area programs as you can.
02. Press Start / Run / %temp% / OK to open the Temp folder.
03. Press CTRL+A to select all the objects and press Delete.
04. Press Yes to confirm sending the selected items to the Recycle Bin.
05. If you receive an error because some files are in use, press OK. Delete as many objects as you can individually.
06. Use Control Panel to open the Internet Options applet.
07. Press Delete Files on the General Tab.
08. Check the Delete all offline content box and press OK.
09. Close the dialog.
10. Open My Computer from the Start menu.
11. Right-click the drive you wish to clean and press Properties.
12. Press Disk Cleanup.