XP/Vista Dual boot 2 drives

[F1]

Check out this article before you attempt anything.

http://www.aiscl.co.uk/dualbootvista.php

[jim532]

thanks for the prompt reply, there is some good information there, but the difference between the article and my scenario is I have 2 pre-existing operating systems on 2 physical hard drives. That article pretty much refers to a fresh install of XP and a pre-esxisting install of Vista.

[TurcoLoco]

It would be best to do a fresh install of both OSes, each one on its own HD, starting with Windows XP first.

But for your scenario, if you can't afford to lose the data on the XP system since you have been using it then, you might be ok by just wiping the Vista drive clean by connecting it alone on the system. Once the HD is wiped clean, then install the XP HD and this blank HD and make sure the hard drive the XP is installed on is in the Primary Master (if both Serial then disregard).
Then boot up the system to XP, format the second drive if it was not done so already, then partition it to your heart's desire. Then put in the Vista CD and when the installation kicks in, make sure to point the installation location as the newly formatted/partitioned HD.

This should work if you have the original Vista CD and also if I did not miss a critical detail...