This is coming from the ItemTemplate for a new class. Go to
[Program Files]\Microsoft Visual Studio 9.0\Common7\IDE\ItemTemplates\CSharp\Code\1033
(possibly a different LCID if you have a non English installation), and you can alter Class.cs inside Class.zip to fit your needs. Then clear out the cache at
[Program Files]\Microsoft Visual Studio 9.0\Common7\IDE\ItemTemplateCache
You should find your classes now get created in whatever way you just altered the template. Keep in mind this is not supported behavior, you are effectively "hacking" VS (although in a very trivial way)
The supported way to do this is to create your own template and use that, as shown here: http://www.switchonthecode.com/tutorials/visual-studio-how-to-create-item-templates