Kinda late, but it could be that you need two sticks for "Dual-Channel" to be enabled. It offers much better performance I've heard, but only works if you have at least 2 sticks of RAM. If you really want to take a stick out, go into your BIOS and figure out if that can be turned off.

I see no reason to run with only one of your two sticks of RAM unless one is faulty. If you're just concerned about temperatures, you should usually just make sure there is little or no dust inside of your computer case. Tidy up the cables so you can get good airflow to the CPU, and have an exhaust fan to push hot air out of the back of the computer. You shouldn't need anything really fancy, but just make sure that the hot air leaves your computer and the temps should drop. You could also just take the side panel off and run the PC as a temoprary solution. I do this at LAN parties if my computer starts locking up due to high temps...mine hates going into 40c...

-Tim_axe