I have an A780L Biostar MoBo, I believe its AM2 which supports DDR2 RAM. How much would it differ form the 64-bit OS? I want to play AC3 but there are issues on its specs.
Hang on, the Phenom 965 is an AM3 CPU. If your mobo is AM2 then it won't support the Phenom CPU. Therefore it won't work.
64 Bit OS is not an issue here, only install 64 Bit OS if you have more than 4GB RAM