You can try to install vista, and then go back in to the Vista installer (via DVD) and just after picking your language, choose repair. To me it sounds like a problem with the Vista boot loader.
Also make sure that after the computer reboots, you do not have any USB devices plugged in, or any Discs in the drive(s). Even if you do not have the boot order setup for USB some computers will hang for a very long time if a USB device can not initialize. Also reset your BIOS to “factory defaults” if the setting is availiable.
You could also install Vista on another PC and then insert the HDD in your other PC (this is annoying as it will require you to activate it because more than 3 hardware items changed).
Anyway those are the 2 things I would try next. Also if you are comfortable updating your BIOS, that never hurts.