Actually only some motherboards require that you install the memory modules in pairs. Since you have three slots it's safe to say that your mobo does not requires this. To try to solve your rendering problem, you should of course make sure that you're not running any unnecessary processes in the background, and also try rendering after a directly after rebooting. If it doesn't help you could try optimizing the memory. Assuming you use Win XP there are a couple of free apps you could try: FreeRAM XP Pro, frees up and defrags RAM. http://www.yourwaresolutions.com/ and PageDefrag, defrags the swap file. http://www.sysinternals.com/ntw2k/freeware/pagedefrag.shtml