For a cheap and great AMD board, you must consider the ECS K7S5A. Newegg has it for $54. One of the great things about this board is its ability to use SDR and DDR SDRAM. Since your RAM is PC100, you can keep it if you match the K7S5A to a Duron. A 1GHz Duron from Newegg is only $43.

For about $100 you can really breathe new life into your machine.