help with voltage settings

[gutsrage740]

I am kinda new to ocing. I have been just tweaking around my rig, its a xp 2800+. Abit NFS-7 Ver 2.0 , 1024 MB of DDR 400, and i have a 400w PSU. I am getting some sort of error with the vio voltage my pc speaker beeps at me when i run 3dmark and have the hardware doc up and it has crashed out of 3dmark twice while running it. I just need some basic info on what the Vio voltage does, how do you set it, and what it should be. Do i need to change my BIOS settings or do i need a new PSU.