There are times when the Windows installer screws up. I'd back out, boot into OS X and use the Boot Camp Utility to delete that partition. Once that's done, restart OS X (not a bad idea when you're messing with the basic structure of your hard drive) and then start the Boot Camp process over again.
I'd also clean the heck out of the Windows CD you're using, just in case the installer had a data error due to a fingerprint or something-the optical drive driver in the installer will work with CD drives older than you are, but it's really, really bad at error detection.