Updated BIOS for Unsupported Gateway

[DemosthenesLocke]

Attempting to upgrade the CPU on my Gateway GT5662. My search has concluded that I should be able to put an AMD Athlon II x4 645 as a few other people have been able to do it. My concern is the BIOS version. Mine is Phoenix Technologies, LTD 6.00 PG, 12/14/2007
MB is MCP61PM-GM AM2 mATX
It is version 2.1.
The eMachine website has a BIOS update for the ET1331g which uses the same MB, while Gateway's site has nothing for my GT5662.
I have even called Gateway and they do offer support for BIOS updates.
I realize it's a old PC but it still performs well enough to drop less than $100 on a new chip...if it'll work.
Do you have any suggestions or updates I could use? I'm not in the realm of modding or Overclocking yet, just something so the new chip will work. (even if that means a modded BIOS version) Thanks!

Win7Pro (64-bit)
AMD Phenom 9500 Quad-Core 2.20 GHz
4 GB RAM
Antec Earthwatts 650
NVIDIA GeForce 9800 GTX

 

[DemosthenesLocke]

Updating my original question: The AMD Athlon II x4 645 arrived and since no solution had been found yet, I decided to try the new CPU anyway. Worst case is I would just have to re-install the old one. The new CPU worked perfectly. No BIOS update needed. Windows can't tell what model the chip is but is does register as a 3.1 GHz correctly. Success!