It can, but you shouldn't install XP that way. What happens is that when you disconnect the drive where you installed XP first, you make the RAID as the primary.
What you have to do is, Install XP first in the drive (or RAID) that is going to be your choice to boot from.
Then run the other XP instalation and install it in the other drive.
I have 2 XP instalations at work this way.
I am not sure what you want to acomplish working like that. Dual boot is usually to take advantage of features that the other OS doesn't have. I don't see any reason why to install 2 XP
I did only because my first OS instalation wasn't working well, and I had been too lazy to unistall it yet
Now, if you already have made the instalations probably the best option is for you to install a boot loader, or manually edit the boot.ini file in your primary partition of the Active drive. Be carefull thought, doing this could make your systems unbootable if you put the wrong settings.

So, for your question, YES, XP can exist in 2 drives (or partitions) without the aid of any boot loader, but the OS itself. But the first OS has to be present in the second OS instalation