I deleted the exported zip file that was placed in my exported templates folder and of course it still shows in Visual Studio\'s \"Add New Project\" dialog. I expected that but
Templates are also stored in "My Documents\Visual Studio 2010\Templates". Under ProjectTemplates and ItemTemplates and so on depending on the language.
EDIT: i just exported a project template. The zip file was created in 2 locations:
My Documents\Visual Studio 2010\My Exported Templates\mytemplate.zip
My Documents\Visual Studio 2010\Templates\ProjectTemplates\mytemplate.zip
deleting both of these also removed the choice from the new project dialog, so I'm not sure what's happening on your machine :(