Re: I think I have lost my mind . . .
Boot from your Vista dvd and select the repair option, it may take a couple times with reboots depending on how badly it's borked.
Sounds like you are using crappy media possibly with a corrupt download, check the md5 against the iso.
Are you burning to dvd and trying to use cd-rom only?
What version of nero? & is much different from 6 for burning an image.