Open the registry and find the key below.
Modify the value of 'AutoEndTasks' to equal '1' to automatically end tasks or '0' to prompt for action.
The default time-out before ending the task is defined by the value of 'WaitToKillAppTimeout' located in the same key, this value is in milliseconds (default = 20000 i.e. 20 seconds). You can therefore additionally change this value to speed the process up.
Note: This change will affect all users but value can also be changed on a user-by-user basis by modifying [HKEY_CURRENT_USER\Control Panel\Desktop] and the same values.
Value Name: AutoEndTasks
Data Type: REG_SZ
Data:(0 = disabled, 1 = enabled)