Locate, and then click the following registry key:
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.
Expand the following registry key:
It doesn't clean up old compressed files, it compresses old files. Double-click on this option to max out the number of days windows will wait to decide whether to compress older files. The max number is '500' days. In my opinion if you haven't accessed a file in 500 days then the ******* deserves to get compressed. heh heh, LOL Default is '50' days, but you could end up compressing files that you need, so I recommend maxxing it out.