I need some help.

I am working on a Cisnet with an Amd Athlon X2 and Nvidia 8600GT and I get the black screen after the WINXP logo.
Its was preinstalled with Windows Media Center.

What happened is that I was scanning my HD for virus and when I came back found a BSOD with IRQL_NOT_GREATER...
Rebooted and got the same error. Could not get into safe mode either.
I figured out and ended up replacing ATAPI.SYS using recovery console from a boot disk I have.
Started getting the black screen during normal booting.
I was able to get into safe mode and in my eternal wisdom decided to uninstall the video drivers so WINXP would reinstall them.
Tried booting in normal mode, black screen.
Tried going back to safe mode, it gets stuck after "Press cancel to stop loading STPD.SYS" goes away and theres alot of disk activity but no boot.
Tried ENABLE VGA MODE and still get black screen.
LAST GOOD CONFIGURATION is kaput too...

I tried to remove the Nvidia card and use the Onboard video (ATI??) and still get the black screen.

The kicker is that in normal boot, I know winxp loads (from the amount of activity of the disk it looks like it shows the desktop) and is working fine. I can use ALT-F4 to shut it down.

This computer didnt come with a disk, it has a secret partition where it keeps the recovery files. I tried using recovery that but because SP3 is installed, the recovery mode cant reinstall windows while preserving the system, it only gives the option to reinstall fresh winxp although it doesnt erase anything, it would require me to reinstall all patches, drivers and applications, etc...

I guess what I need is somehow refresh VGA drivers or Nvidia drivers using recovery console or using ULTIMATE BOOT CD which loads winxp from CD giving me access to the HD.
Any help would be appreciated, thanks