to start, open 'my computer' rht click on the drive, properties, you will then see a button 'disk cleanup'
also worth going via internet explorer, tools/options, delete browing history files etc. Next, do a search for all temp files, use *.tmp, you will be safe to delete them, 1 or 2 might not allow you to delete, they are in use, log files.
SD, November 2011