Windows Vista/7: Start > search for gpedit.msc. Navigate to Computer Configuration > Administrative Templates > Windows Components > Windows Update and enable "No auto-restart for scheduled Automatic Updates installations".
All non-Home users can apply the same policy change by adding a new key to the registry. Go to Start > Run/Search for regedit. Navigate to HKEY_LOCAL_MACHINE SOFTWARE Policies Microsoft Windows WindowsUpdate AU. Create a new 32-bit DWORD value named NoAutoRebootWithLoggedOnUsers and give it a value of 1.
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A piggy bank of commands, fixes, succinct reviews, some mini articles and technical opinions from a (mostly) Perl developer.