It doesn't have a cpu installed,it was called a barebones computer.
The seller on ebay said it was am3 socket?
Do you need more info to help?
Problem #1: You need to replace the motherboard to use a new CPU. Since HP, ASUS, Dell, Compaq, etc. Computers that are already assembled have locked BIOS's. So basically if you make any hardware changes... You would be screwed. other than changing the graphics card.