It's been dual-booted with a 32-bit and a 64-bit Vista? Check the boot sequence in BIOS, I always use 1 USB, 2 CD, 3 HDD. I think maybe they dorked something and it needs the bootloader on the cd to start up. To be totally honest, I would send it back, or if you want to void your warranty, just reformat and only put 32-bit on. 64-bit software is still in the works in most cases. In theory, most if not all 32-bit software should run in 64-bit environment, but we all know Windows is a lot less than the theoretical results. Unless you have a specific need for 64, there's no need for it.
Now that I'm thinking about it, FIRST boot from the cd into the repair utility, and log onto the 32-bit vista if you have a choice.
type the commands "fixmbr" and "fixboot" at the command line (separately, but I'm sure you know that).
after that type "chkdsk /p /r" to check for any other system file and boot errors
Best of luck! post back or pm me if you need more advice.