just so you know, you can only legally have that serial key that accompanies your disk running one PC with Windows ME at a time. do you have the retail version of ME or the upgrade? you should enter your bios, set your drive to boot from your optical disc, then restart your machine with the disc in the drive. you'll reformat the hard drive you want windows on (so backup important data first), and then install it. be sure to have your serial key on hand. FYI, google and the search tool are your friends. this has not only been answered all over the net, but on AD a nearly infinite number of times. nobody wants to spoonfeed the same old crap to anybody.
you skipped my bit about spoonfeeding, didn't you? >.< please, for the love of god, just search for a little bit before you come asking for help. be independent; it's nothing but good for you.