PLEASE HELP! boot issues.

hi, i'm not too sure if this is where to post this but here goes?
system is,
mobo: GA-EP45-DS4P
CPU: intel Q9450
RAM: Kingston KHX8500DR2K2 - 1066Mhz (4 x 1 GIG)
HHD's: 2 x 500 gig W.D sata, running in RAID 0 (windows xp)
1 x 500 gig W.D sata (storage)
everything was running fine until i tried to add a terrabyte HHD in this morning.
initially i got a "DISK BOOT ERROR" right after the post pool varification. so i fiddled around with my connections etc, unplugged the new HDD and my optical drives and windows started to boot. i turned off system, added new HDD, windows started to boot, i turned off system and reconnected opticals, now when i tried to start up again i got a "restetting bios successful" message during post and that was it, after pool initialisation i get windows couldn't boot system 32 file missing or corrupted.
i tried to reinstall on a spare drive, just to check out what's what, and i get a bsod stop error as soon as windows finishes installing files.
i've had similar problems with other machines and it's always a RAM issue, so i pulled out all but one stick, no good, i've been into bios and everything is set ok, RAID 0 is working.
i flashed bios from F5 to F7, still no good.

hope that all makes sense

please help, i'm 2 weeks from end of uni semester, need my pc BADLY!

thanks in advance for any replies.