Nigel
You overlooked the Event Viewer System log.
To access the System log select Start, Control Panel, Administrative Tools, Event Viewer, from the list in the left side of the window expand Windows Logs and select System. Place the cursor on System, select Action from the Menu and Save All Events as (the default evtx file type) and give the file a name. Do not provide filtered files. Do not clear logs whilst you have a continuing problem.