This label <label> is used by a previous version of <File or Project>.  Remove the old label?

A VSS label is used to identify a particular version of a file or project. 

This error has the following cause and solution:

• You are attempting to assign a label to a file or project, and another version of that file or project has the same label.

  Click Yes to apply the new label and replace the old label. 

  Click No to cancel the action; the old label will remain.

  Click Cancel to cancel the labeling operation.