I’m seeing a lot of people still using some old ways ported from TFS 2008 to delete a team project like TFSDeleteProject utility.

In TFS 2010 the administration tasks are made very easy to help you in a lot of administration stuff, for the deletion point specially you can navigate to the Administration Console then Select Team Project Collection

• Select the project collection contains the project you want to delete then navigate to Team Projects.
• Select the project then click Delete, you will have the option to delete any external artifacts and workspace too.

Hope it helps.