You have your FSB set to 100(200) or 100x10=1000. The Sempron 2400+ is a 166FSB CPU and it's multiplier is 10x or 166x10=1666mhz. Set the jumpers to 166(333) via the mobo booklet. If it's anything like my two Chiantech KT-600s, it'll be on the front side of the board next to the IDE connectors. Some KT-600s have this option in the bios, either way, read your booklet and set it right. You chould even overclock it by setting it to 200(400) or 200x10=2000mhz. But you may need to boost the vcore about 5%-10%. This is what one of my 2400+s is OCed at without any vcore boost. What brand KT-600 do you own?