WinXP Media Center (basically XPPro)

Last night got the need to restart to apply patches message, so I shut the box to give it an overnight rest... well this morning it hangs during boot. Won't run in safe mode, safe mode with command prompt, enable boot logging, enable vga mode, last known good config or debugging mode. I've tried booting from Dell recovery CD, the WinXP CD all to no avail.

During safe mode boot agpcpq.sys appears to be the culprit, but I can't get to any point where I can get a dos prompt to fiddle with system.ini, win.ini or rename the offending driver to get past it. There's lots of web articles pointing to this driver as a fault point. None of them have an actual viable solution.

I've tried repair from Windows setup CD based on an MS article that talks aout disabling agp440.sys but that never gets past (I gave up waiting after 10 minutes) examining the second sata 1TB drive I added. I can open the box and unplug the second drive it's just data storage, but I'd rather not if I don't have to.

Booting to the Dell diagnostic CD doesn't get the C: drive available.

I have just updated the BIOS from A05 to A07 and still no joy.

WTF else can I try to get to a C: prompt so I can get the box back up?