hi Chungachoo,
i tried to use the exact same card in my Asus P4B266-C mobo, and the second i would put the card into the mobo, the darn reg light would pop up. as you mentioned, the computer wont budge at all. however, once i put my older geforce card in, the light goes away and the computer boots just fine.
i think it's crazy that it has to be this way, but oh well, what can you do but buy another video card.