You can, but you still need to have a board and bios that allows that. It seems to only support the athlon/sempron series, so there must be something about the board that prevents it from being able to use the Phenom series. Pure guess, its an early AM2 board and can't supply the power that the phenom needs. I also vote it won't work.
^Right, you can install an AM2+ processor in an AM2 mobo, BUT if that mobo support the processor. In your case, the mobo support many models of Athlon and Athlon X2 series, but your specific model isn't supported, that's why you can't install the processor.