What type of processor do I have???

I bought an old P4 from a friend and it would not work in a new M\B that I purchaced so I had to buy a newer P4 for the M\B. The guy at the M\B factory told me that it did not work because the processor is first generation. And I would need another old M\B that would support the voltage of this CPU. Where would I find a M\B that would work with this CPU? and what would I ask the person selling one to ensure that it will support this CPU???
Also what is the name of the CPU (Wellington perhaps) I can't remeber. I want to use this to upgrade my little girls computer.

Thanks for the help,

B