Customizing VS.NET 2005 Templates
This is a great article on customising VS.NET
The following is where VS.NET stores the Item Templates:
C:Program FilesMicrosoft Visual Studio 8Common7IDEItemTemplatesCSharp1033
It is stored in a zip file. I am not sure.
This is a MSDN article on customising the templates (as is this).
This is an article on adding your own template items.
