That's all the
RAM that a 32 bit
OS can see. If you can get x64 to work then it will see all 4GB. I would try either Vista or XP 64 bit and everything should be fine.
The problem was the cmos needed to be cleared. I had you bump the voltage because from my experience
RAM tends to like a little more when using 4 sticks. I dunno maybe it's just me.
Also I am running vista ultimate on another
PC here and it is working great, so I wouldn't worry about it not working with your hardware.