If you designed a menu in AE, and also need a highlight layer, here's what to do.
Go to an appropriate frame and choose Composition>Save Frame As>Photoshop Layers .
Open the file in Photoshop.
Turn off the visibility icon for all layers which are not part of the Overlay
Select one of the visible layers, and choose Merge Visible from the layer palette submenu.
Lock the transparency for this new merged layer by clicking on the Lock transparent pixels box.
Choose Edit>Fill and fill with Black (or White, depending on your DVD application).
Create a new Empty layer and place it in the background.
Select All and Fill this layer with White (or Black, again depending on your DVD application.
Delete any unused layers.
Choose File>Save As and save a flattened PICT or TARGA file to create an overlay layer. Again, you don't need to save layers or alpha channels.
Save the layered PSD file in case you have changes.