|First of all, sounds like you are guessing on what may be wrong with the computer. |
The link you provided above spells out the socket type.
"Processor Socket 754 for AMD Athlon64"
IMO it isn't worth putting any cash into. If you pull the heat sink off and look at the labeling on the processor you can determine what it actually is.
The specs you link to state the board is designed to run Athlon 64 CPUs. Look at the link below for some info on socket 940 processors.
Your link also has a processor support list, which doesn't include Opertons or Athlon 64FX processors.
In short, the system is outdated and not worth putting cash into. Especially when you don't know what is wrong.