To delete a Work Item, please follow the steps below:
1. Open a Command Prompt window and then direct to the "IDE" directory for your installation of Visual Studio 2010/Visual Studio 2010 shell. In the example, it is "C:\Program Files (x86)\Microsoft Visual Studio 10.0\Common7\IDE".
2. Enter the following command:
witadmin.exe destroywi /collection:https://s01.tfshosted.com/tfs/Organization_ID /id:WorkItemID
Note: Organization_ID is the name of your collection and WorkItemID is the ID number for the Work Item.
3. When you're prompted for the credentials, enter the administrator user name and the corresponding password.
4. Enter Y when it ask you to confirm the action.
Now your work item has been removed from TFS server.