1) It often needs to be the EXACT same RAM, but sometimes works if not.
2) SWAP around the sticks and test the other RAM by itself in the same slots.
3) Look for a BIOS update for your motherboard
4) Be careful to ensure each stick is fully seated
5) always run Memtest
*Also, if still having issues with FOUR sticks (8GB total) and all sticks were working (two at a time) and tested with Memtest, try dropping the memory speed manually in the BIOS as far as it goes. Never leave it like that. It's just for troubleshooting.
If nothing above solves your problem you may have a bad RAM slot on your motherboard. Unfortunately you can's simply test one slot at a time. You can only have a single stick in one of the four slots (see motherboard).
Yeah I got it figured out Dimm slot 0 is bad, so I got 6Gb I'll just have to get a 2x4 set and sell the 2 sets of 2x2, and actually you can test one slot at time cause thats what I did,took dimms from 0 and 2 and it booted with 1 and 3, took the same sticks put em in 0 and 2 and no boot,pulled the dimm from 2, no boot,moved a single stick to 2 and it booted.But thanks for the help!