What socket?
what specific type of CPU is it?
what size case is it going in?
ATX...
Micro ATX...
does it hasve to have an AGP slot or can it have built in only graphics?
if this is a pre-built "company"branded computer, i.e. Compaq, gateway, etc. ,,,, it may be more complicated than you think...
be more specific with what your looking for, and you will have a better chance of getting what you need...