(don't ask me how I know).
Price - within your pocketbook.
Match processor with motherboard as in choose the processor then find a motherboard that accepts it.
Choose speed, core. Do you need a dual core or single core? Dual core is good for running several high intensity processes at once. Single core is good for 90% of average users.
RAM - match it with the motherboard. One Gig is fine, two Gig close to overkill. Above two Gig is for bragging rights only unless you are trying to decode the human genome.
Hard and optical drives - most motherboards today have both IDE and SATA ports. Match the board to your existing drive types. Don't get a full SATA board if your drives are IDE, they won't work together.
Video, audio - If you have on board video and audio, find a board with the same. If you have cards, find a board that will accept what you currently have. If you have on board and want to upgrade to cards, find the motherboard that will accept sound and video cards of your choice. Video cards come in many flavors and unless you are a hard core gamer, 128 Meg of video RAM is enough. Same with sound. Unless you want to run digital out with surround sound, a standard board is fine. I bought a full blown digital sound card with optical out and 7.1 surround sound. I've never used the features.
Dialup - need a modem? Most motherboards do not have built in analog modems.
Ethernet - the newer boards have Gigabit LAN ports built in. But they work with all, 10/100/1000, LAN facilities.
Have fun.
Wayne
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Any suggestions on a good and easy to install one? I am not real good with this stuff so it has to be easy.

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