The fastest CPU for that mobo is 2.0 GHz, if you have BIOS 14 or later.
The board can NOT be overclocked.
It uses the (expensive) RDRAM.
The speed difference is not worth it.
Keep that system as a (reliable) backup and build yourself a nice new system with an AMD64 socket-939 processor. You can go all the way and get a board with PCI-express (or SLI) graphics and DDR2 memory.
A bit cheaper is going for a board with AGPx8 graphics and normal DDR memory.
The likes of Abit, Asus, Gigabyte and MSI have good boards here.
You will need a fairly powerful, good quality PSU for this.
Plenty of posts on this subject in this forum.

 

Thanks for the advice buddy

 

Recently I was a similar situation. But I wanted to add more ram. After looking at the price of RDRAM, it was so expensive that I decided to go the whole route as RBS outlined, and got a new Socket 939 motherboard and an AMD 64 cpu. Granted it cost more than the ram would have, but at least I applied that money toward upgrades with the future in mind. I got a new motherboard, cpu and ram, look at my profile to see what I opted for.