upgradeing processor on an AM2 mobo

Since your motherboard is not a standard commercial motherboard, it was customized by Compaq, you will have to try and find out what CPUs Compaq sold your model with. Since you have to use a Compaq BIOS and not a generic BIOS the choices may be limited.
 


It came with an AMD Athlon 64 3800+ 2.4 gig single core. I did see on ebay a AM2 socket 2.2 gig dual core processor that should work with it though for 30 bucks and am thinking about going that route as ultimately I'd like to build a new system with mobo that can take more than 4 gigs of ram and load XP onto the current system to play retro games on