Help with Bios CPU support

Hi,

Wonder if some one can help me out.

I have a motherboard MSI MS-7225 and wanted to use it with a CPU Athlon 64x2 4400
but everytime it boots it says that the CPU revision is not supported. It does boot in to windows but I have to exit the bios settings every time.
I been reading about updating the bios and adding agesa code to make it compatible.

Can some one please give me instructions on how to modify the bios or point me in the right direction??..

Thanks for the help in advance...