Save even more money by getting a refurbed nForce board at newegg for about $30. Put an 1800+ on there and clock it to 2400+ speeds on a 174MHz fsb. Total cost about $75, add in $15 for a decent heatsink.
You should be able to sell your P4 board and cpu for at least the same $90, no money spent. This cpu will beat the stock 2400+ that only runs on a 133MHz fsb. Not to mention it will smoke the P4 at 2133MHz, all for free.