Hi, I have a new PC build with a 500gb hard drive and every day without me installing anything it loses 6 to 10 gig! I figured it was a virus of some kind and installed an anti virus program and scanned the PC but it reported that it found nothing. Once this happened i thought it would be better to just reformat and start all over hoping that it wouldn't happen again, after reformatting my vista ultimate 64 it did the exact same thing it started at 16 GB and now at present its all the way up to 43 GB with out me doing anything. why is it doing this? How can i stop it?