Ken's link is good. But what ever RAM you get, run Memtest86 on it over night. I see so much flaky RAM these days. Like 1 out of 16 sticks is bad. In one case I had 3 out of 8, and then when those were replaced 1 more bad (Crucial later admitted they had a bad batch). It doesn't matter the maker. After finding a couple bad from Corsair I went back to Crucial (since both Tyan and Supermicro recommend them), but same thing there. It's just that today's memory densities are so high, there's bound to be flaws in the manufacturing.
The same for hard drives, every maker has had a bad batch along the way, and every brand I've used I've had premature failures with. So now I just stick with Seagate, and run RAID for the important stuff. When a disk fails, I buy a new replacement, but still return the broken one for warranty. They almost always send referbs as replacements. I put those in less important machines--but now that I think about it, I don't believe I've ever had a referb disk fail; maybe I'm doing that backward.
