Adding more ram to s775 system advice

[IvanDobskey]

One of my friends has an old s775 PC with an abit p35 based mobo. He currently has 2x1gb geil ram and wants to upgrade to 4gb. His PC is not overclocked or anything. Would he be OK to add another 2x1gb of a different brand of ram? I'm fairly sure this is OK as long as it is the same spec?

 

[IvanDobskey]

I think its pc2 6400. Not sure on the timings though. Can't seem to find any 2x1gb geil kits so it'll have to be a different brand. No problems using all four ram slots on a p35 board?