Computer locking up in BIOS?

[InorganicMatter]

My system has been rock stable until recently. The last thing I did was lose the SATA RAID array and implement a SCSI arracy. After that, it all went to hell. The system is unstable, Windows is giving missing components (brand new install), it locks up when navigating the BIOS, and sometime it will not accept any keyboard commands when booting up and I have to reset a few times to get it to accept commands. Sometimes it locks up as soon as it boots.

Sounds like a bad PSU, huh? Nope. I disconnected every peripheral, all that's powered is my motherboard and CD drive. Same thing. Not the CPU overheating either, the temps are reasonable. What's up? System specs:

Pentium D 820
3GB DDR2
Adaptec 2100S controller, 4x74GB SCS-160 drives
Windows XP

 

[TheMostWantedPolishTwin]

run memtest86 to check the memory..

 

[InorganicMatter]

run memtest86 to check the memory..

It's now locking up as soon as BIOS finishes. Can't boot to anything.

 

[PigCorpse]

Tried clearing it with the jumper?

 

[DeChache]

Pull out the Adaptec 2100S controller and see what happens.