When you enter the Windows Update site, your PID (Product ID) is checked for validity. If the PID is not valid, your Windows 2000 installation is presumed to be a pre-release version.
If you are running a retail build, your PID is missing or corrupt.
The easiest way to fix the problem is to perform an update install:
1. Boot the setup media.
2. Choose to Setup Windows 2000.
3. On the next screen, choose R for repair.
Performing an update install will not damage or adversely effect your installation.
NOTE: Alternately, you could use tip 2268.