One is CL 8 and the other is CL 9. That could invite problems.
Best case scenario it would slow down the original set to match the added set and not complain to you. Worst case scenario you have to take the old ones out and just stick with 8 unless you want to mess with settings.
Probably more likely to work in the best case scenario kinda way, but it is kinda an oldish board too so maybe 50-50ish.
However, the question probably does need to be asked, what are you trying to do with this extra RAM to begin with?
WEll basically i am just trying to keep my PC up to speed. I DO some moderate gaming..not TOO heavy..but ya, i play BF3, and LOTRO, and other MMOS, also i like to use video editing software, like sony vegas, and recording gameplay with FrAps.
Also even when i am not gaming at all, it seems that my machine is runnning 1.83 GB of physical memory, according to task manager. And there are many times, while i am am gaming (especially if i need to Alt-TAb to check something online) That windows 7 "detects" low memory, and wants to reduce my performance.
Anyhow i think 8GB would be fine for me. But, i already have the 4 GB, so if i could, id like to use it for more power i guess. But if it would negatively affect my performance by having both, i suppose i can just try and sell the older RAM, or maybe build a lower end PC one day for my parents or something..