XP won't retain various system changes

My 4 month old install of XP Pro SP3 (slightly NLited) appears to not be retaining changes - it's is behaving as if I were installing new apps and updates in a virtual environment like Sandboxie or Returnil. The changes disappear when I reboot.

Examples: I've installed the newest Windows updates (KB969947 and Nov Malicious Software Removal) several times, via both Automatic Update and the Update website. They install correctly, tell me to reboot, and when I do, they're gone.

Avira updates disappear after every shutdown.

Comodo Firewall recognizes my recently created home home network at every startup even after I set it to allow my computer to be accessible on the network.

I have Returnil installed on my machine but it is not turned on.

All advice is appreciated, as I assume I'll have to re-install if i can't figure this out, and I'd rather not...

 

Hello, smilejack1, I would suggest you head straight for the Malware thread, by following this link: http://forums.majorgeeks.com/forumdisplay.php?f=35

Look at the 4th link down, and click onto the Sticky: READ & RUN ME FIRST. Malware Removal Guide . Follow those steps, and try to do each one. If one doesn't work, don't stop, go n to the next. If you get an error, be sure to write it down... Our Malware Team is the Best, and I think it would be best to start there, to find out if your problem is malware... If it is clean, then we will go on to another solution, but if you have malware, it is going to be almost impossible to go anywhere here..

Also, do you have your OS discs? It does sound like you have something going on there, and that is the place to find out what it is, and where it is.

 

I've completed the malware removal procedure and attached the logs, with the following qualifications:

SAS said it found no malware and produced no log.

MGTools displayed several error messages unlike those mentioned on the "Using MGTools" page, and I found no file named C:\MGlogs.zip on my drive, even though MGTOols said it would be there. I took a screenshot of the command window and the error messages and have attached it.