Black Screen of Death caused by a malware in XP

Hello,

Tonight i recived a call from my brother telling me AVG had found a virus and could not remove it.
I told him to boot in safe mode and run AVG and spybot to try and remove it. When he caled back he said all he had now was a black screen nothing else. As my brother is not computer savvy iv brought the offending box round here.

I'v booted into safe mode where nothing loads but the mouse curser. Then tried to access task manager with ctrl+shift+esc but just recive a window saying "Task Manager gas been disabled by your administrator."

I really dont know where to go from here other than formatting but i thought you guys might be able to help me get to the read and run me first stage.

Thanks in advance.