My Dell Dimension 2400 runs only on 2 512 sticks of RAM. But I would like to test it on a 1.5 or 2 GB if given the chance to acquire another 1 GB DDR RAM. They are quite expensive nowadays and hard to find. Since its just running on XP for light tasking, it runs better today compared before on a 512 module. Having the same computer model, I have seen threads online that have used a total of 2 GB max of RAM on that dell machine. Just a thought on how I added the other 512 stick. The lone 512 stick was on the 2nd slot and when I added the other 512, it makes a beep code/message for the changes or new hardware installed. Making it unbootable. Removing/Clearing the CMOS battery and swapping places the two RAM on slots went smooth after.