|I doubt the problem has anything to do with not using RAM slots 1 &2, but if the HSF is blocking the slots, it's a poor design. Why would you install a massive cooler (or water cooling) if you're not overclocking? Do you have the stock AMD cooler?|
Make sure your BIOS is properly setup. Do not simply run defaults. Manually configure your settings, especially the RAM voltage. The JEDEC standard calls for DDR2 RAM to run at 1.8v but much of the so-called gaming RAM or performance RAM requires higher voltages...2.2v or higher in some cases. Use the RAM manufacturer's settings, not the BIOS defaults.
"Just looked in system info and states i have installed 4gb memory and have available 2.93"
Are you sure you have a 64-bit OS?