Whats the correct BIOS setting for a SCSI raid (dell 620)

m2v files on SCSI Raid - play slow, then very fast

My Dell 620 workstation (yeah, its old) has just gotten pissed off at me.
Its my editing system, and the m2vs/DIFs (movs) are exhibiting weird behavior;
they will play slow for a few seconds, then they will play sped up. This is in Windows Media Player/ or Quicktime.

I had recently got another (removable) internal Hard drive installed (ATA), but that shouldnt interfere with a separate SCSI 160 raid, should it?
Should the wrong BIOS setting affect a SCSI raid? (this seems to ring a bell, but I dont know enough about it)

Are there any VIDEO editors out there who know about raids, and who have seen this behavior? Seems to only afffect vid clips, as my audio files are playing fine.

Wheres Dr Le when I need him?

I am wondering if the video clips are corrupt, as I tried copying them to the new ATA drive, and they play back with the same problems.

Any suggestions folks?