Here's a link to a tip by John Wilkinson that might help your situation:
Hope this helps.
I have 2 320 gb SATA harddrives. XP on one and Vista on the other. i want to dual boot from both harddrives. my master drives is the one with vista nd the slave is the one with xp but in order to boot into xp i must enter my BIOS settings and tell it to boot and thats quite annoying. Ive tried Easy BCD and VistaBootPro to create an entry but it never works. it juts acts like XP is never there. please help me dual boot!!!!!!!