Have you got each drive on its own individual cable. I have not yet used sata but with raid you can only have one hard drive on one ide channel. Which is the same principal.
Try setting the pc to boot up with just one hard drive connected. Install XP fresh, dont try and recover/ repair it, it is faster just to wipe the hard drive and start again. Install XP into a partition about 8 GB big. Then partition the rest of the drive how you like.
Get the pc up and running. Then when all is ok. Then connect up the second hard drive. This is where you will have to change the hard drive raid settings. This is upto you now. You could have it set up so that it thinks that 2 drives are as 1 ( striped??) or set it up as mirrored so that whatever happens on the first drive happens on the second. Good for back up.
Anyway just try the above with 1 hard disk and see where you end up.