Thanks for replying. I knew that all the RAM would run at the lowest speed. I just wondered how much difference a higher RAM speed would make.
My guess is not enough to make it a priority in terms of upgrades. Perhaps not even enough to bother with after priority upgrades have been done.
More memory should help for some programs, or with heavy multitasking, but probably isn't crucial considering I already have 2GB.
My top priority upgrade is a video upgrade. I have 2 GB of RAM , and a quite adequate processor (Athlon 64X2 5200), but I only have on board video.