I have an ABIT NF7-S that uses the Silicon Image 3112 RAID controller. I have Redhat 9 and Windows XP installed on a single RAID-0 array using two Seagate Barracuda 80 Gb SATA drives. I partitioned the array in half (80Gb WinXP, 80Gb Redhat 9).
I installed Windows XP first on sda1 and then I just went to Silicon Image's site and downloaded RAID drivers for Redhat and followed the instructions. I used the "closed source" drivers since I am not confident enough with linux to do the open source thing. Besides, I just wanted it to work.. I don't really care about open source.
Finding the drivers is tricky.. you have to search for drivers on SI's site to get to the correct page. By the way.. if you used NTFS for your XP install, you won't be able to use LILO or GRUB as you bootloader. There's huge issues unvolved in installing it correcly. I've tried it several times, and eash time I've ended up unable to boot anything (redhat or XP). Each time, I had to restore the Master Boot Sector with the XP CD.
Let me know if I can help. Write me directly at email@example.com