problem with installing SAP Portal Add-in 2.5 for Visual Studio 2005.exe

Hi

I'm trying to install "SAP Portal Add-in 2.5 for Visual Studio 2005.exe" but it gives the following error message "asp .net web application must be installed".

My system has

winXP OS,MS VS 2003 and MS VS 2005 i have also installed PDK.

What could be wrong? Or did I miss any thing?

Thanks.