>>> I always pull the plug when shutting down
If you do this AFTER shutting down the computer that is fine, but pulling the plug on a computer that is running is a sure way to wreck the hard disk or the operating system (or both).
A computer needs a tidy shut down to ensure everything closes down properly, pulling the plug does not do this.
The reason the fixes seem to come when you shut the computer down is that Windows can only update certain files DURING a shut down (or start up) as there are certain files it can only update when Windows is NOT running.
It is VITAL to leave Windows update running and installing fixes as many of these will be security fixes and if you dont install them you are leaving yourself wide open to virus attacks.