OK, first - in 2003, there pretty much was just one standard kind of DIMM, an unbuffered ECC type. So, if it is your brother who might be purchasing this for you, you can count the pins or gold teeth at the bottom of the RAM stick for him, he can tell this to the salesman at Fry's or wherever, and you are pretty much likely to get a matching chip. (No parity errors.) (If in doubt, count the number of pins on one side of the notch on the bottom, and then count the number on the other side.) (And, Kingston Economy is a perfectly good DIMM at a reasonable price.) Second, for XP Pro, its probably best to accept the automatic virtual memory settings, - just leave it be. In general, your virtual memory should be three times the amount of physical RAM on your system. XP Pro generally can detect your addition of a new RAM stick and adjust the virtual memory accordingly. A few times when I've built out a new system, it has failed to adjust it, so you might want to check. For your drives, are these three logical drives on a single physical drive, or are these two or more physical drives?