hi, when i got vista i installed it on my spare SATA hdd and i had xp on the other, what i do now is open up my pc and switch the hdd's around so if i want xp to load i would only plug in the xp hdd and leave the vista one out and just do it the other way if i wanted vista, but i take it you dont want to keep doing that,
im not sure if this might help but when you boot up your pc, go into the bios and select the boot prioity bit, then sellect what hdd you want it to boot from then restart
that might help but i would get the pros advice if im wrong
