if the computer came with ME then it should have a restore CD or partition. You should be able to run that and getting a fresh install should be pretty straight forward.
However, once you have a fresh install of ME, you'll still be running ME! I would strongly recommend upgrading to XP, or windows 7 if your PC can run it (post specs and we can tell you).
I had ME on my old P4, upgrading to XP was the best thing I could have done for it.