The only way to reinstall Windows ME is to find a new copy of an install disk. You will have a hard time locating a clean copy from Microsoft as it is an old operating system. Contact the manufacturer of your computer and ask them for the refresh disk.
The only way I know to re-install any windows version is if you have the disk. If you do not have a disk but you have the product key you can call microsoft up and they will send you a disk for a nominal fee.
Unfortunately you will need to get another copy of the disk from somewhere. You may be able to borrow a copy from someone but it may ask for a serial number before it will install. So you might have to get a full version online or somewhere.