1) Open a command window. (Click Start, click Run, type cmd, and then click OK.)
2) Navigate to the directory of the Aspnet_regiis.exe version you want to use. Remember that each version of the .NET Framework comes with its own version.
The file is usually located in the following directory:
for XP c:\windows\Microsoft.NET\Framework\<versionNumber>
for 2000 c:\winnt\microsoft.net\framework\<versionNumber>
Then type aspnet_regiis.exe -i