Sub RenameFile()
  ' Before running the code, click Tools > References in the Visual Basic Editor and
  ' make sure that "Microsoft Scripting Runtime" is checked.
  Dim strPath As String, objFile As File, sName As String, sNewName As String, sNewPath As String
  Dim objFolder As Folder, objFSO As Scripting.FileSystemObject
  
  ' Put your path here:
  strPath = "C:\Users\username\MyFiles\"
  
  Set objFSO = CreateObject("Scripting.FileSystemObject")
  If objFSO.FolderExists(strPath) Then
    Set objFolder = objFSO.GetFolder(strPath)
    For Each objFile In objFSO.GetFolder(strPath).Files   'Loop through all files in the folder
      sName = objFile.Name
      If Len(sName) > 16 And IsNumeric(Left(sName, 5)) Then   'If file starts with 5 digits and has a name longer that 16 characters
        sNewName = Trim(Mid(sName, 16))
        objFSO.CopyFile strPath & objFile.Name, strPath & sNewName, True
        objFSO.DeleteFile (objFile.Path)   ' Delete the original file
      End If
    Next objFile
  End If
End Sub