The best way to test RAM is with memtest.
http://www.memtest.org/
Download the bootable ISO and mount ( burn ) it to a cd. Then in BIOS change the boot order to DVD/CD drive first and your computer will boot off the burned disk. This allows memtest to run outside of Windows and test 100% of your RAM.
Free burning tool if you need one.
http://www.imgburn.com/