Windows 2000 and Windows ME both suck?
Why don’t any of your laptops run Windows ME or 2000?
To make a long story short - because they’re inferior operating systems. Microsoft released Windows ME prematurely and as a result, the operating system had tons and tons of problems and bugs. To combat this, Microsoft then released a revised version of ME that it called Windows 2000. Windows 2000 is the same operating system as ME, just fixed up a bit. Honestly though, they both just suck. The system itself is unstable and unreliable - which is why Microsoft worked around the clock to produce Windows XP so quickly afterward (2001). We choose not to install Windows ME or 2000 because of these problems.
from here