I don't think it's a problem with your RAID drive, though I've never used a RAID drive so I don't really know. However, after having read many threads about dual booting and problems, it seems to me that there is a problem with your grub file (grub.conf I presume--I use LILO so I'm not too sure--and I think RH uses grub by default). Anyway, it would seem as though it's not configured to recognize your XP partition.
Could you provide a bit more information no how your drives are set up? For instance:
/dev/hda = XP
/dev/hdb = CDROM
/dev/hdc = RedHat
/dev/hdd = DVDROM
I'm quite sure this isn't the right set up, but an example anyway. Check your grub.conf file to see if the WinXP drive is listed as one of the options to boot. It doesn't sound like it is. Since I have no idea what your hardware set up is like, I did a search for grub.conf
here at LQ to see what I could come up with. I've never used grub, so looking at the grub.conf files don't really explain much to me, but maybe for you, some of these links will prove helpful. Keep me posted and I hope this helps.