I know it will run slower but I just thought I'd double check. Because if you put FSB wrong in a 266FSB Mobo it just shows the slower speed. So surely the cpu will just run slower. I'm just building a crappy lil pc out of spare bits (can u tell ) to play videos for my daughter. The chipset is even worse, dirty Sis crap. Somebody agree and I'll stick it together now. Cheers guys.