You will need to gain the service manual for your computer. I have no idea what an e-Machines is, but they will have it either on their website on your computers page, or by request. This will list everything compatible for your machine.
Its a good idea to link your machines webpage when opening a post.
Well, I thought this would be an ATX PC, but its a TV box. No the CPU is soldered to the motherboard, RAM and HDD are the only upgradeable bits of it. I'm strangely craving one of these for myself now