Exactly? No, because I have a different BIOS...
Hmm, I'm running out of ideas...
It might be worthwhile to see if your BIOS version is the latest available. If not, an upgrade BIOS image might do the trick...
The only other thing I can think of is that XP won't see the disk as a single unit because it has not been formatted... When I've installed RAID on LINUX and XP, it's always been a matter of creating the physical drive from the disks and then formatting. The creation of the file system comes last...
A chicken and the egg problem...