I'm building a computer, but I still need a little help. ?

it appears all with work from the cpu motheboard side. some motheboards like only a specific memory from certain manufacturers, so you should check that hte brand of memory will work with your motherboard. You should opt for faster memory - as fast as you can afford. Memory is cheap so you should add as much as you can afford. vista is a pig for memory, so since you are using vista, you should load up on memory. You can get away with the 2 gig, and add more later if you think it is too slow.