Finally if you open 'command prompt' (found under 'accessories' in the start menu) and then type,
'Cleanmgr/Sageset:1' (without the quotes) and then press enter...
You'll then see a box appear and you'll need to tick every check box you see inside the panel, then click ok.
Then type:
'Cleanmgr/Sagerun:1' (without the quotes) and hit enter. Vista will then run through a more thorough clean. Do this on a regular basis to keep system running in good order.