Re: is 512 and 256 compatible?
It'll work out just fine. I have PC2700 and PC2100 RAM in my computer, the PC2700 just gets clocked down to the PC2100 speed. It doesn't matter what kinds of ram you got in there, if you have a stick of 512 in PC3200 and a stick of 1 gig of PC2100 then the PC3200 will get clocked down to the latency of the PC2100, but you'll still have 1.5 gigs of RAM.
What I'm saying is that no matter what kind of RAM you stick in, and by kind I mean like PC2100, 2700, 3200 and so on, just make sure your motherboard supports the amount you want to stick in, like my motherboard only supports upto 2gigs of RAM at PC1600 all the way up to 3200. The only thing you need to be concerned with is whether it's DIMM or SIMM, I think it's called SIMM, and how many pins it takes and so on...