You probably [SECURITY PROMPT, DO YOU WISH TO CONTINUE?] need to find [ARE YOU SURE YOU WISH TO CONTINUE?] Vista certified SATA [ARE YOU REALLY REALLY SURE?] controller drivers for the system.

(Sorry, couldn't resist poking at the annoying "feel good" security prompt crap in Vista).

Check the motherboard makers site and the SATA controller site for possible drivers that may work with Vista. Odds are the motherboard is running the boot drive in a sort of compatibility mode to get the OS booted.