Norton keeps shutting down

My roommates computer does not have any pop ups, i got rid of them all a long time ago, but I think he might have a trojan that shuts norton antivirus off. I did all the steps, online trojan scans, adaware, spybot, spyware blaster, ccleaner, McAfee Stinger. I've also run Norton in safe mode, nothing detected. I think the Trojan he has is the ByteVerify trojan, it keeps being cleaned, and then reappearing. I have to reinstall norton and then it shuts down again. When i reinstall it, do a virus scan, nothing pops up, but usually a day or two, it says it has deleted the ByteVerify trojan, than after a few more days, Norton doesn't work and it says the files have been corrupted or their is an internal error in the program and that there is a license problem. I haven't written down where the files were located, and I can't get to the logs for Norton, so I have no idea where the trojan pops up. Does the ByteVerify disable anti virus software or could there be another trojan or virus on the computer or could it just be that my CD isn't copying on his computer right? He has a Dell Dimension 4500 with 2.4 ghz P4, 256 RAM and Any help would be appreciated.

 

Forgot to include that he's using windows xp pro and that I disabled system restore and did all the steps in safe mode with networking as well.

 

I just ran Bitdefender again because I haven't ran it in about a month, and it found a trojan dropper that I thought was already fixed by House Call I believe. Anyways, I think this trojan renamed itself and is in the Windows/Bundles folder with the file names 32wu54rd, bs5-vwqouc, icDW1, optimize and setup_silent_17125. Should I delete these files right now with system restore, safe mode with networking, or should i restart into just safe mode and delete them, I think these files were deleted previously and I obviously don't want them to replicate itself somewhere else.