Windows 7 doesn't require any tweaking other than normal settings changes. It works against you.
It is normally other errors logged in Performance-Diagnostics nearby Shutdown degradation Critical/Error that will clue you to what app or driver is causing the issue.
You can try Clean Boot Procedure to see if you can isolate the cause: How to Troubleshoot a Problem by Performing a Clean Startup in Windows 7 or Vista
Also check for issues cued and Generate a System Health Report at Advanced Tools menu at Control Panel\All Control Panel Items\Performance Information and Tools\Advanced Tools.
And check for Problem solutions by typing Problems in Start box.