The default time for the system to issue the 'did not respond' message is 5 seconds.

You can adjust the time by setting the HungAppTimeout Value Name, a string (REG_SZ) data type, at HKEY_CURRENT_USER\Control Panel\Desktop, to the number of milliseconds desired.

NOTE: See the AutoEndTasks and WaitToKillAppTimeout Value Names at tip 0033 » Can't shutdown without "killing" an application.