[Crusader]

Like I said, my experience is mostly with servers, not so much with home PCs, so your mobo may not "suck". At any rate, in your case, you need to find the documentation on your motherboard and find out the max number of RAM it supports. Even if it has three slots and 2GB sticks fit, doesn't mean your mobo supports that amount. When you know that number, your memory should be the same quantity in each slot to match that maximum size. For example:

Motherboard max RAM = 3072GB
RAM slots (DDR, SDRAM, DDR2, etc.) = 3
RAM you should put in = 3 sticks of 1GB (1GB = 1024, 1024 x 3 = 3072)