How does one turn the plot overwrite option back on as shown in the screenshot attached?
This setting is stored in:
C:\Users\<username>\AppData\Roaming\Autodesk\DWG TrueView 2015 - English\R13\enu\Support\Profiles
in the file: FixedProfile.aws
There remove the section for:
<HideableDialog id="AcPlotGui.PlotFileExists" title="Plot - Plot File Exists" category="Plot" application="" result="6"><Preview><TaskDialog Source="/AcTaskDialogs;component/TaskDialogs.xaml" Id="AcPlotGui.PlotFileExists" xmlns="clr-namespace:Autodesk.Windows;assembly=AdWindows"/>
As alternative you can also delete the whole roaming folder structure from TrueView and the registry section:
HKEY_CURRENT_USER\Software\Autodesk\DWG TrueView\R13
This starts the 2nd stage windows installer service which restores the original files.
regards
Markus