It looks as though my resources were incorrect, as far as the two motherboards having the same processor socket.
(MSI RS480M uses a Socket 754)

What does concern me, is if the motherboard chipset used is the same. This was the stated information.

The motherboard chipset consists of the Northbridge chip, and the Southbridge chip.

Chip, and Chipset are slang terms for IC. Integrated Circuit.

http://en.wikipedia.org/wiki/Integrated_circuit

Viewing this motherboard diagram may help explain how the motherboard chipset comes into play,

http://en.wikipedia.org/wiki/File:Motherboard_diagram.svg

[You can also type, one at a time, Northbridge (computing), Southbridge (computing), Comparison of AMD chipsets, in the Wikipedia search bar, to gain more knowledge]

The Northbridge chip determines what Processors can be used.
It also controls high speed graphics technology.
AGP and PCI Express being high speed graphics, not PCI.

Determines what Ram Memory is used, and what Southbridge chip is compatible with it.

Let's go back to basics, and see what Northbridge chip is on your motherboard.
Two ways.
One, it looks as though you may be using a tiny program such as CPU-Z, or Belarc Advisor.

If not, I would advise downloading the free, tiny program CPU-Z from CPUID.com
Can you install the old processor, (AMD Athlon 2.25GHz), and get your computer to work, or are you using it now?

After you have CPU-Z running, left-click on the Mainboard tab, and tell me what it states for Chipset. Also tell me what it states for Southbridge.

Second way.
Physically look at the Northbridge, and Southbridge chip. IF, they are not covered with a heatsink.

The Northbridge chip is usually a large chip, and is located close to the processor socket.
Most configurations are like this; Processor socket at the top of the motherboard, ram memory slots to the right, Northbridge chip below the processor socket.

Motherboard designers put the Southbridge chip all over the place. There is no usual spot.

It is my belief at the moment, that your Northbridge chip will not support dual core processors, such as an AMD Athlon 64 X2 4400+
Only Single core processors.
Once I know what Northbridge chip you have, we can determine what your CPU support is.

BIOs should've came pre-installed on your motherboard. If not you'll need to put a CMOS battery into the slot, it looks like a big watch battery about the size of a nickel.