XP to Vista: dual drives

I have been reading with great interest the material on double-booting XP to a Vista system since I have a new copy of XP media center with both service pacs and a "hot rodded" Vista computer. I also have 2 new hard drives,one 160gbt and a 320gbt, to use. I would like to use the 160gbt drive for the XP system partially because it is a PATA interface simplifying procedures as the Vista drive is SATA and I'm certain I'll need the larger one on Vista much sooner. Now my problem seems to be the initial boot changes since nothing I have read really covers the way my boot setup "looks" right now. I cannot seem to do much with it. The BIOS is a common AMI and the computer is a Compaq Presario SR5210NX. PLEASE HELP!