If you have windows 2000 running on your system, then I personally would not purchase and install windows NT 4.0 unless you want to take a look at it and learn something about it.
It is possible that if your hardware is too new, then you may have problems finding drivers for it. Also NT does not have USB support.
You cannot compare NT to ME they fit different purposes - business vs home.
The righ comparison would be win95 or NT...( but still fit different purposes)
If you would like to upgrade the OS and find something better then ME, then get XP Home.