IS 2010 can't get past start screen

Hello and thanks alot for helping us!

I have an XP machine in my home network that got infected with IS 2010. When I start the computer (in safe or normal mode) i get a fake welcome screen (the blue Windows welcome screen) with the "administrator" button. I am sure its fake because I see the desktop "flash" for a split second before the fake screen covers it. I can't get past this fake start up GUI to take your recommended countermeasures. I just need a clue so I can get "in" and get this scourge out! I am a veteren of fighting the AV 2009 war so I know something about these things. Anyway, I have already taken one interesting countermeasure. Since I couldn't get past the fake start screen, i removed the hard drive and attached a raid to USB adaptor cable. I then cleaned the drive by scanning it with MBaum from another machine thru the USB connection. Both Mcafee and MBaum found numerous infections and cleaned them. But upon retrying I still get the fake screen when I reboot with the cleaned drive in the first machine. I repeated the cleaning procedure and the infections had regenerated. Any ideas how to get past the fake screen or to clean remotely with the 2nd machine?

Thanks
John

Is task manager disabled? (ctrl + alt + delete)