Whenever we rename a file in Visual Studio .NET, the file becomes a new file in SourceSafe. If the file has been checked-out, the status of old file will remain as checked-out in SourceSafe.
The step by step to rename a file that under SourceSafe control:
Figure: Warning message of renaming files under source control.
Figure: You are seeing this as the new file name already exists in SourceSafe, just click "Continue with change".
Visual Studio .NET should find the file under source control and it will come up with a lock icon