Many times .NET 2003 installation fails due to some known / unknown reasons. And while installing it again it might ask you to install prerequisite first even though you have already installed it. You would become confused why it asks me again and again to install prerequisite. Possibly because of installation failure it might have updated wrong registry entries.
The possible solution is...
Go to Start > Run. And write following command line to run the setup file.
And you are done! It won’t ask you to install prerequisite any more...