Strange
Could be that the cable is not with the blue end in the MB connector and you are jumped for CS, but I doubt it. It could be the PSU, not enough juice and when you added the second drive into raid that taxed it out. But I dont know. Have you looked at the logs and the device manager for these. My guess is that it is related to XP and a reinstall is going to be needed. Rclick on my computer then manage and look at the event and application logs in the event viewer and the device manager under properties for each drive and for the IDE ATA/ATAPI properties, check out disk management under storage.
On the RAID you can not do what you want if you are running RAID0 which I would guess is what you have. With 0 you write interleaved and would need to do a new install.
Edit just noticed the floppy part. Have you tried disconnecting the floppy and then booting and seeing what you get. It could be a bent pin in the floppy connector, or the floppy cable in really wrong. Backwards will usually give a sustained floppy lite.