NET Framework 2.0 SP1 requires that Windows 2000 Service Pack 4 be installed on your computer before you install .NET Framework ...

.NET Framework 2.0 SP1 requires that Windows 2000 Service Pack 4 be installed on your 
computer before you install .NET Framework 2.0 SP1. You can download and install this service pack from http://windowsupdate.microsoft.com/. After you install this 
service pack, you are required to restart your computer. .NET Framework 2.0 SP1 setup  
will not automatically restart. To restart .NET Framework 2.0 SP1 setup, double-click 
setup.exe on the CD, DVD, or network share you installed from or click the 
appropriate link on the download Web site.