Ask him what version of bios he installed.
You can look at the info for the board and try to find a similar setup from asus and try the most updated version.
Make a mistake, and your motherboard will be ruined.
Motherboard Name Unknown
Motherboard Chipset Intel Lakeport i945P
System Memory 1024 MB (DDR2-533 DDR2 SDRAM)
BIOS Type Award (05/18/05)
Video Adapter ATI Radeon X300/X550/X1050 Series (128 MB)
Motherboard DMIMOBO: ASUSTek Computer INC. P5LP-VX
Motherboard DMISYS: Sony Corporation VGC-RA840G
From another thread talking about your computer. I would not necessarily trust that info and run cpuz as MMike recommended to confirm.
Then good luck finding a compatible bios to flash with.
My personal opinion on a computer of that age, put the old working cpu back in. Cut your losses and save for an upgraded computer if possible. Next time you can build and have better upgrade options in the future.