"Gigabyte K8NS Socket 754 motherboard"
My sources say GB K8NS is a socket 939 board, which would be in accordance with your CPU. If you get beeps, your CPU does work. You can use either a 32 or a 64-bit memory configuration. Check the possible memory configurations on page 15 of your mobo manual:
http://europe.giga-byte.com/FileList...pro-939)_e.pdf
To eliminate possible AGP problems, you could borrow any old PCI display card and insert that into any of the standard PCI sockets. I'd take the board out of the case and test it alone with only the display card installed. Use a cardboard box or similar as a stand. A jumper block can be used as a power switch.