Since this is an old board, my knowledge is limited on this one.
But i will tell what you can try possibly, till someone else gives some more light on this.
Try to boot the system with one CPU.
Update the bios to the latest one.
If your board is the ddr1, then the latest bios is Build 0075: P09.00
Else if the board is the ddr2 version, the latest bios is Build 0019: P03.00
Once you have done that, try to check if it makes any differences. The reasons why i told you to update the bios is because the new bios had fixes for new support for the cpu with fsb 800Mhz.
Make sure to read the read me how to update the bios.
All the best,