I have a PowerSpec, too! Not the same model, but it has regular RAM slots, for sure, and I can't remember ever seeing RAM hardwired on the mobo. It should be there near the CPU...
If you care to know how much of your current RAM is being used by PCLinuxOS, try running free -m
in a terminal. In any case, 256M sounds like a stretch, alright.
[alan@chickens ~]$ free -m
total used free shared buffers cached
Mem: 4005 1471 2534 0 89 649
-/+ buffers/cache: 731 3273
Swap: 5992 0 5992