Many customers ask me about deleting Work Items from the TFS.

Here is how to do it for TFS 2010:

Step 1: Log-in to the TFS using a TFS administrator user.

Step 2: Open a command line and go to:

32bit machine - “X:\Program Files\Microsoft Visual Studio 10.0\Common 7\IDE”
64bit machine - “X:\Program Files (x86)\Microsoft Visual Studio 10.0\Common 7\IDE”

Step 3: Use the “witadmin.exe destroywi” command in the following way:

witadmin.exe destroywi /Collection:http:\\[ServerName]:8080\tfs\[CollectionName] /id:[WI ID]

you can add as many Work Item IDs as you like using [,] for example 54,88,92 etc.

You can disable the prompt message by using /noprompt.

For deleting work items in TFS 2008 see:
http://blogs.microsoft.co.il/blogs/eranruso/archive/2009/08/10/delete-tfs-work-items.aspx

Have Fun!!!