Burn In is when u let ur computer run games or programs that makes ur CPU work hard, for a long time. And Yes u can use 3d Mark 2001 as a "burn in" program, just let it loop the demo, and leave it the night over. Burn in can help when overclocking. I don't think anyone knows why, but in some strange way, it can make u able to overclock higher. Some believe in burn in, and some dosen't. I believe in it, cuz when I gort my Duron, I could only run it at 900MHz, fter some burn in, I could run at 978MHz.