Build Suggestions?

Hey guys, so I spent like 70$ ish dollars in total on this build really. Yeah I know how is that possible. Well my dad gave me one of his old PC's from his work that had MOBO with AM2 socket, 3GB of RAM (DDR2), and a crappy Single Core proccesor. So I gladly took the old PC and added a AMD Athlon 64 4400+ which I then overclocked to 2.8ghz with stable temps, and a GT 630, and also overclocked that quick a bit aswell. I spent about 70 dollars in total I think, 65 for the GPU and 5$ for the CPU on ebay. Does anyone here know of any quad core AM2 processor, with atleast 2GHz or more? Keep in mind, I'm 13 so money is a tough object for me, as my parents don't give me money for this because it is a "waste of time".

You might be able to use an AM3-socket CPU with that motherboard with a BIOS update, what is the model of your motherboard?
AM2/AM2+ mobos can be backwards compatible with AM3, but only certain motherboards have the update, if I'm not mistaken. (Which I very well could be.)