Dell Dimension E510 here, xp media center sp2 also.
Same problem here with the safe mode -> a blue screen (not THE blue screen, btw) with an odd looking prompt and a question mark. Not a real prompt, nothing blinks.
Except on mine I can't get into windows any other way. It'll just hang at the logo screen with no hdd activity whatsoever.
Just spent couple hours cleaning this thing of trojan.generic, winlogon86 and some rogue.antispyware.antivirus. Seemed to be running ok. Then did 2 things before last reboot:  set page file back to 'system managed size' (it was set at custom and much larger than recommended), and  installed windows update 'office xp service pack 3'.
Edited by homersimpson, 07 January 2010 - 08:36 PM.