Depends on what's wrong with it really. Does it even boot? Does it make it past the BIOS screen? Do your fans turn on but nothing else? Could be something simple like a bad connection with something, or your CPU died, etc. Maybe you power supply is failing and not giving enough voltage? Try and eliminate stuff 1st to determine a board is at fault. If it has something faulty like a soldered chip with 100 something pins on it you'd be better off just spending 50-100 for a newer better board. There are some pretty decent boards out there for this price. I'm running a A780L3L Biostar board I bought in a set up somebody built. They run for 50 on some online sites. It's a mid level board I believe. I put my old HD from an ASUS A7LM2N-LA (HP Pavilion) on this and after some updates and an OC of 3.72Ghz I'm satisfied for now. It handles a max of 8Gig RAM DDR3. The BIOS is extremely easy to flash if you ever need to. There are definietly better boards, especially if you want a chip to produce more than 4Ghz of speed. But for the price of a used PS3 game, I think it's a great deal. The A780L3G board is the next one up from this and can handle x6 core AMD chips. This one is rated to x4 cores, but it does have a 5th core area to enable (Assuming you'd have to buy an x4 and try unlocking it to see if a 5th core might unlock).
Anyways, if it's an older ASUS, you're probably better off replacing it. I have 2 ASUS boards just sitting as one pooped out after buying it on Ebay to replace the 1st one I bricked. Had I known now what I didn't know then, I would've just upgraded the board altogether to a better one instead of wasting 70 bucks for another that died in 4 hours.
If you run into trouble swapping, this site is by far one of the better ones to get advice on. If you're dealing with HP/Compaq and are swapping boards, I just went thru the ordeal and can give insight if needed. Good luck!