I have Visual Studio 2010 Professional, and I've been using the TFS service at visualstudio.com. I've read this question and it's answer as well as other things around the web. However, TFSDeleteProject doesn't seem to be part of my development toolset.
So, how can I delete a project?
Since TFS @ visualstudio.com is 2012 based, it's best (and sometimes required) to perform administration functions using Team Explorer 2012.
Regardless of whether you have 2010 or 2012 installed you'll find the EXE you are looking for in:
C:\Program Files (x86)\Microsoft Visual Studio XX.0\Common7\IDE*
*Substitute (x86) and XX.0 as needed
Additionally you should have a Visual Studio 20XX Command Prompt shortcut in your start menu. Running that will create a CMD session with the above directory in the path.