How can I figure out what's compatible with what, to build my own computer?

As in what graphics cards and what motherboards go together, or processor and motherboard? Or any issues known for different combinations. I'm planning on using a 32 bit Core i7 processor, running Windows 7 Professional, and am not terribly sure on the rest. It will be a gaming machine (and I'd like very much to use dual graphics cards if possible), along with being somewhat of a server (lots of storage). What I'm looking for are compatibility issues and reliability ratings you might have. Alternatively, if you know of a site that I've not found, to find these sorts of things, please let me know. Please don't exclude any type of components either power sources, hard drives, cd/dvd combo drives, pretty much anything you might find in a typical gaming machine. Also, I'd like any and all recommendations on what to use for anything other than the processor and the OS. I'm not sure what I should be using. Thank you all very much.