Dtrickster Garden

On an NTFS partition, Disk Cleanup can compress old files
to save space. But calculating the savings and performing
the compression often take a long time, and on some systems,
Disk Cleanup hangs during the process.

If that happens, or if
you don't care to wait, use the Registry Editor to disable the
compression:

Delete this key

HKEY_ LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Explorer\VolumeCaches\Compress Old Files.