If I follow you correctly.

Vista things it's installed on a RAID 0 configuration. Meaning both drives act as one large drive. Vista has a RAID Driver to see this drive correctly (especially when you install vista like I just this this morning).

You installed XP but uhooked a drive to do so, breaking your RAID configuration so to speak.

So now want Vista to Book with a RAID 0, and XP to boot using No RAID at all.

I'm not sure that's really possible. You have removed half of what Vista is expecting to see and put XP on it in another partition. Your RAID 0 is likely broken beyond recovery.

The right way is to use your RAID 0 configuation and set up a dual boot arrangment using partitions on the single hard dive that Vista and XP can see. Each only expects to work within it's own partition and each see's the RAID 0 configuration like they should.

You may be able to boot from either drive if you turn off your RAID entirly, but I don't know that for sure.