It says there is no options for processor speed. You could however lower the RAM timings, that will help by 1% or so...
Or page 73/74 it talks about BIOS recovery, where it says compares CPU version to BIOS, this to me sugests that there may be a editable BIOS, where you can change CPU information - as long as someone made one.
IMO you should just leave the PC, or get a new motherboard that is ATX and supports your CPU socket - use CPU-Z to find it.
Cisco CCNA, Comptia A+, 1/3 through CCNP