can I install .net 3.0 extensions on Visual Studio 2003?

The extensions for .net framework 3.0 (templates to create .net 3.0 applications, like WPF, WCF, WF) only work with Visual Studio 2005.

You may look at this site https://www.microsoft.com/downloads/details.aspx?FamilyId=F54F5537-CC86-4BF5-AE44-F5A1E805680D&displaylang=en under the system requirements.