Full format reinstall xp - virus still here.

I have had some sort of deeply rooted problem with my computer that wont go away. i've reformated the hard drive several times with deletion/security programs and tried just about every forum and software to remove this thing and for some reason it wont go away. Basicly the malware hijacks my browsers and puts advertisments in the script of every page i visit.
I want to put an end to this virus once and for all and I dont think a simple reinstall is going to do the trick.
HERE ARE THE SYMPTOMS

VERY HARD TO DETECT THAT I EVEN HAVE MALWARE
Windows NT shutdown when trying to terminate certain processes
Windows NT user has control over every part of system
Changes to registry dont stick
COMBO FIX fails to work
MB does not detect anything
Hijack this deletes bad entries but the re create themselves
Can not log on as administrator
Virus reinstalls itself upon windows re install

Anyone out there have a clue as to what sort of bug this is??? , my best guess is that it has tricked the system into thinking its a component or has overtaken the system as a ghost driver.