Turn off your comp..and take your current stick of ram out. Notice that it has either 1 or 2 U-shapes in the bottom(in b/w the gold plates) for guiding the chip in the right way. this will tell you what type of ram you need. IF it has 2, you need the older SDRAM, which is a little cheaper right now, but slower. If it has only 1, you need the DDR ram, alot faster, and only slightly more expensive. I agree with the other posts...you will DEF see more bang for you buck by going to 1gb ram.