If what you want to do is replace the board with a newer board.
The first thing you need to do is define your needs.
Form factor: AT, ATX, NLX, LPX
What CPU do you desire to use: AMD, Intel, VIA/Cyrix?
Do you want to reuse RAM or CPU from the existing board?
Once you decide what you want, go to the hardware review sites to compare different MBs. One site is www.tomshardware.com
Specific recomendations depend on what you use your system for, and what buying options are available to you.
ASUS, ABIT, EPOX, and Intel are my preferred MB manufactures. But, if you ask 10 IT people for their choice, you will get even more to choose from.
You should be able to identify what you have now from the BIOS ID. www.motherboards.orghas a list that you can use to cross BIOS IDs to MB manufactures.