Depends on Ur MB & apps.U sure

How old is your motherboard? Are you sure it can take advantage of PC3200 RAM? If it only can go as fast as PC2100, your PC3200 will be used as PC2100 anyway. If so, go for capacity and put both in. If your MB can go up to PC3200, and you need the speed for gaming etc., then leave the PC2100 out. If you need to open a lot of apps simultaneously, then go for capacity. Your best bet is to find out what the max speed your mobo supports and buy two match RAM sticks for that speed.