Backdoor.Tid!inf virus not removing

I originally had the MacAfee suite (which is free with Comcast) and this virus got past it.  It downloaded several other Trojan viruses and malware (or malware infected with other viruses - there were fourteen instances of five different Trojans in all) and rapidly made my computer unbootable.  I then purchased Norton Internet Security, and by using that and repeatedly reloading Windows managed to remove all the malware except this one.  (Oddly, although MacAfee couldn't stop it and Norton can't remove it, both list it as a low level threat easily removed.)  I can run the computer for short periods, but generally not access the Internet except when booting the Norton CD, although I have managed to activate and update.  NIS says if I have problems I should boot into safe mode, but in safe mode I get a message that NIS cannot launch in safe mode.  It does run a very short scan, but does not find or remove the Trojan.  After a week or so, I've given up on removing the virus with a single drive.

 

So I've now purchased another hard drive and plan on doing a clean installation of Windows on that, then later connecting to the infected drive, cleaning it, moving the files I want, then reloading Windows (in case I later need to boot from that disk) in a clean partition.  My OS CD is Windows XP SP1a. 

 

Anybody see and problems?  Will NIS stop this virus from infecting the clean drive, or must I leave this disconnected for a few months until Norton progresses toward dealing with this virus?

 

I should say I'm reasonably pleased with NIS, since an up to date MacAfee could not stop this virus from infecting a fully patched Windows XP SP3 and Norton has at least made some strong gains against it.  But I'd like any advice as to how best to fight this infection.  (I'd also be interested in knowing why the two biggest names in the anti-malware battle list all five viruses as low risk and easily removable considering my experience...)