For the few people that can’t hibernate their computer because it automatically resumes, or the ones that just don’t use hibernation, you’ll want to disable this since the feature consumes as much hard-drive space as you have in RAM. A simple command prompt entry can disable hibernation.
1) Click on the Start Pearl > type cmd in the Search Bar > press Ctrl+Shift+Enter
2) Enter powercfg -H off
Once hibernation is off, you’ll still need to use Disk Cleaner to get rid of the files stored on your computer for previous hibernation sessions. To access Disk Cleaner:
1) Open the Start Pearl again and type cleanmgr in the Search bar.
Windows Vista will then prompt you to choose the partition you wish to clean. Select the desired partition, and the rest should be pretty straight forward.