When a virus kills "Hijack This" ... is it over?

My Windows XP has gotten hit by a monster virus of some kind this weekend: In a matter of seconds it wiped out most functions. It won't even shut down apart from using the power switch.

"Hijack This" freezes in mid-analysis, and displays a box with the message:
"This action cannot be completed because the other application is busy. Choose 'Switch To' to activate the busy application and correct the problem". ...so I can't copy & paste the few files it has listed.

The only clue I have is that this one file:

C:\Program Files\Common Files\System\apcsvra.dll

is where Avast freezes when scanning (since the other programs don't display filenames when they freeze-up, this is the best I can go on). System Restore is gone, "My Computer" can't be accessed; only a few rudimentary functions remain.

If I can break the source of the free-ups, I can at least run an HJT on it and hopefully get to the root of the problem. Is the "apcsvra.dll" file OK to delete (or at least move to a temp file)? I've run SpyBot, AdAware, AVG, and Avast, & deleted all the TEMP files I could get to.

I'm out of ideas & resources at this point... does anyone know of a way to deal with this?

Thanks.