My hard drive just mysteriously fills up by itself, the first time it happened I got a message that my system restore would no longer be able to function. I hurriedly started removing games to provide more space. The next morning it was full again. I was running Windows XP home, PC-cillin, and Webroot at the time, I have since installed Avast from Computer Shopper recommended downloads. But scanning shows no problems found. Now have Ad-aware and Spybot. None of the programs show anything wrong but the hard drive fills up continuously. Rebooting clears the hard drive of the mysterious files. Please Help.
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Have you searched with windowsExplorer for NEW or LARGE files created recently ?
Ran a large file search and came up with this C:WINDOWS\system32\LogFiles\WMI\trace.log and it was 10.6 GB. Rebooted and it went back to zero. Is this more of a problem with an Windows application? I will check their data base to see, but I do not usually have much luck with their solutions. Hope you can still advise.
Your suggestion sent me in the right direction. I put the file name in Google and found out that it is from using Bootvis from Microsoft. Not a virus or worm or Trojan my system is clean. At least I now have Avast because of it. Thanks.
Welcome to the forums and the best av service available! 
Glad you got your problem fixed and that it wasn’t something major such as a virus, worm, etc. 