Re: asus p4p800s
The only compatible processors with that board I can find are P4s and Celerons, so there is not much upgrade room.
I did find that it can support up to 3.6 GHz though, so if you can find a Socket 478 P4 with 800 MHz FSB with anything up to 3.6 GHz, you should be good to go. I don't see the need for upgrading that though unless you have something that is a lot less.
My Computer: eMachines T5226 - Intel Pentium D Dual Core @ 3 GHz - Diamond Viper Radeon HD3870 OC Edition with 1 GB GDDR3 VRAM - 4 GB PQi Turbo DDR2-533 RAM - Corsair 650W PSU with 52A on single rail - TSSTcorp DVD-DL+-RW combo drive - Lite-on 52x CD-RW burner - Creative SoundBlaster X-Fi XtremeGamer - Logitech z5300e speakers - WinFast TV Tuner - Vista Ultimate 64-Bit. eBay name: Flightsimboy304