What Mark said. Don't keep the old sticks around. Just get one or two 1Gb sticks. Using more than two pieces of different size, different brand, different speed RAM never did give good results, at least in the old days. I'd suggest overbuying for now so you can maybe reuse it in your next system (if you upgrade more than once every 2 years).

Kingston Value RAM has never done me wrong, but neither has Crucial. Crucial was much cheaper years ago; I'm not sure what happened. Also, I think Crucial and Corsair are one and the same. A few major RAM names are from the same company, but I get them confused.

On an odd note, I don't know if they still make "registered DDR RAM" anymore, but I'd recommend it. I built two identical machines, ABit KG7 Athlon 1.4, but mine with registered DDR and my friends with regular DDR. After 2 years, his RAM burnt out. Apparently, ABit boosted the default RAM voltage or something just to claim they had better performance. 4 years (?) later, my registered DDR RAM is still humming away while Google Groups reported many cases of burnt regular RAM. It's worth it to get good parts.