OP, I expect you will not have a problem. The problems some have cited above in going from 2 x 2GB to 4 x 2 GB on an Socket 939 Athlon 64-CPU system are related to how the Athlon 64 CPU's handle RAM. That CPU family does its own RAM management within the CPU, and it is known that they have to slow down slightly when fully loaded with 4 RAM modules. I have a machine like that. However, as I understand it, mobos using the P4 chips handle RAM outside of the CPU, with dedicated RAM management chips on the mobo. You can check the manual for your system, but I expect the mobo-based RAM management system you have will NOT have to make any odd adjustments when you add RAM. It should automatically keep on using Dual-Channel operation.