Vista - Install failed rollback failed

I installed RC1 with online updates on my dell 700m laptop and it got all the
way through to completing install, then I guess it tried to load Aero or
something and just went blank. I forced a reboot and it said rolling back to
previous operating system. I then gave it another try without online
updates. This did almost the same thing, took a bit longer ( about 2 hours)
and then the display went blank again. Forced reboot after about 12 hours of
waiting, tried to rollback and failed. Now I have a cmd prompt and nothing
else. It appears that the rollback was removed (windows.old not there?) and
that the install log shows it copied stuff from $windows~bt to \windows so
i'm guessing I have no way to rollback. I fooled with bcdedit and got it to
try to load into the /windows dir but it still thinks it is in an install and
tells me to reboot and reinstall. There is no option to continue the install
which was an upgrade, and the upgrade option is gone for me now. should I
just buy a notebook ide adapter and pull any files off that drive and give up
on the possibility of the upgrade/install completing? Is there a registry
key somewhere that i can set so it thinks the install is complete?