white hawk, go to your motherboard's manufacturer web site - they should have a list of tested, compatible memory. Then, buy memory from that list. Of course, try the less expensive on-line places to get the memory, if you buy direct from the memory manufacturer you pay too much. If you are rich, spring for the cas 2 pc3200 memory, otherwise, grab 2 sticks of cas 2.5 or 3, they will work great either way. CAS 2 is better, especially if you overclock, but cas 3 if just fine for the average person.