When I attempt to shutdown my computer, it often requires me to press "End Task" in ccMail. I mostly see the issue around 16-bit applications (yes they still exist). The following Windows NT \ Windows 2000 registry changes will automate the "End Task".

This will change it globally for all users on the box.
Hive: HKEY_USER
Key: .DEFAULT\Control Panel\Desktop
Name: AutoEndTasks
Type: REG_SZ
Value: 1

This will change it for any particular users on the box.
Hive: HKEY_USER
Key: your_user_id\Control Panel\Desktop
Name: AutoEndTasks
Type: REG_SZ
Value: 1

NT default is to wait 20secs. To lessen the wait, you can change the WaitToKillAppTimeout value found in the same subkey in msecs. Don't set too low or you could lose data.
Name: WaitToKillAppTimeout
Type: REG_SZ
Value: 20000 msecs=default

Background:
When you issue the shut down command, NT sends shutdown requests to running processes. In particular, 16-bit applications running in the VDM (Virtual DOS Machine) often do not honor the shutdown requests. If an application does not respond to the initial shutdown request, NT prompts for a decision

• kill the task
• wait for the task to die on its own
• cancel the shutdown