What do i do now??

When selecting my mobo and ram i chose the 512 x 2 pc3200 kit because my mobo supported up to 3 gb of 400mhz ram.

My problem is, i recieved the mobo via fedex today, opened it up and read the manual and the manual says that it only supports pc3200 in 1 DIMM slot, DIMM slot 2 supports pc2700. But i have 2 sticks of 3200, what happens if i put both sticks in? Thanks, this is the first computer ive built so im new at this and dont want to mess anything up to bad.

jeesh sounds like someone is playing games describing ur board. the main thing is will it overclock past 2700. my abit ic7 supports pc3200 but runs easily up to pc4800+ so see how the memory runs. if it doesnt run well i would think about replacing ur mb with a board designed for pc3200..

will it harm anything if i just use both slots w/ 3200 in it and dont oc it or anything?

what motherboard is it?

I'd select a different mobo. This day and age should support full DDR 400 in ALL DIMM slots.

Nothing bad will happen to your machine if you put it in, but it might end up underclocking both sticks of ram if you use both DIMM slots.