Can't reload Vista into Parallels Desktop 7

Windows Vista got corrupted after it had been loaded into Parallels Desktop for Mac, v 7. I'm on a MacPro (MacPro1,1), running Mac OS 10.7.5. I uninstalled old Parallels and associated Windows Vista; reinstalled Parallels Desktop for Mac, to include the latest update. Booted Parallels, tried to install Vista from DVD, entered Product Key, and then got error message that it can't be installed - notify Parallels support.

What might be wrong? Any ideas?

Thanks......Jim Taylor