Ruined My Boot Camp Install

I installed Parallels 3.0 to use the Vista Ultimate installation that I had on the Boot Camp hard disk. The program was laughably slow, however—honestly leagues worse than Virtual PC. I don't know how this could get rave reviews; it couldn't even load a website in my Windows install.

Anyway, I went to boot back into Windows using Boot Camp, and it doesn't work anymore. It initializes the Windows install but then restarts and boots into Mac. Moreover, my boot screen is now utilizing a lower resolution (equivalent to the "full screen" version of Parallels).

I uninstalled Parallels, but the problem persists.

Please help me, as I don't want to find out my money spent on Windows is lost.