i've did this about 100 timeS b4 with windows 98SE and i'm positive windows ME is the same.
First partition in 2, Second install windows ME, ounce finished run win2k setup and choose clean install NOT UPGRADE and you should have both OS's running. Just choose your OS at the bootup screen after your computer has gone throught the BIOS check.

Note that you will have to install any programs you wish to use twice, i usually install my programs in win9x first then reinstall the programs in win2k into the same directory to save hard disk space