Hi I am more than a little out of touch, in the past I have built my own machines but not the last 2 computers. I teach software development. I have a ASRock AM2nF3 VSTA mother board and 1GB. I want to increase this. The Manual says 4-DDR11 DIMM slots and supports DDR11800/667/533. I am using XP and the memory is OK, but I am using Fireworks, Dreamweaver and Visual studio all at the same time! so time for more memory. There is little difference in the price so which 800,667 or 533 is best. Any reason other than cash flow to choose to 2, 4 or 8 GB? No games all work and no play! - dull??