A week or two ago I had ~20GB free, and then I installed a vista service pack update, and when it was done my free space had jumped up to 80GB. I go WTF and check to make sure everything was still there, it seemed so. I restarted and ran all my scans, nothing bad and it stayed at 80. But I've been watching it, and it's been going back down, a few GB at a time, now I'm at 60GB and I don't know what's going on. If it was just a few GB I would have assumed it was just cleaning up old updates presumably in the service pack, but 60GB is bigger than the whole operating system. And there is no way I've used 20GB in a week. Help?