Symptoms: 1) the computer stops responding (hangs). When this symptom occurs, a teal or black screen may be displayed. 2) The computer does not turn off when you receive the "It is now safe to turn off your computer" message. 3) An error message is displayed on the screen.

Causes: 1) Faulty or incompatible device drivers. 2) System services that either do not respond correctly or send busy request messages to the system. 3) Faulty or incompatible programs.

Solution: 1) Use Task Manager to Identify the Cause of the Shutdown Behavior. Use Task Manager to determine the programs that are currently running on the computer. For each program that is listed in Task Manager, manually quit the program, and then shut down and restart the computer to test if the shutdown problem is resolved. 2) Undo Any Recent Changes to the Computer. If the shutdown behavior occurs immediately after you make a change to the computer (for example, you install or upgrade either a program, a service, or hardware that has device drivers), undo the last change that you made. 3) Use Safe Mode to Identify the Cause of the Shutdown Behavior. When you start your computer in safe mode, only a minimal set of essential drivers and services is loaded. Safe mode is a useful diagnostic tool to use when you want to identify and resolve problems that are caused by faulty drivers, programs, or services that start automatically. If the computer shuts down correctly when it is in safe mode, restart the computer in safe mode, and then open the boot log file, Ntbtlog.txt, and then make a note of the devices and services that did not load when you started your computer in safe mode. The Ntbtlog.txt file is located in the %SystemRoot% folder (by default, this is the Winnt folder). 4) Upgrade the Computer's CMOS/BIOS. Incorrect or damaged CMOS and BIOS settings can cause startup and shutdown problems. To confirm that the computer's BIOS is current, contact the computer manufacturer to inquire about the latest BIOS update available for your computer.

 To prevent users from shutting down the computer from the Log On to Windows dialog box (CTRL+ALT+DELETE ), you can make the Shutdown button unavailable by using Group Policy.

1. Click Start, and then click Run.
2. In the Open box, type gpedit.msc, and then click OK.
3. Expand Computer Configuration, expand Windows Settings, expand Security Settings, expand Local Policies, and then click Security Options.
4. In the right pane, double-click Allow system to be shut down without having to log on.
5. Click Disabled, and then click OK.
   NOTE: If domain-level policy settings are defined, they may override this local policy setting.
6. Quit Group Policy Editor.
7. Restart the computer.

To edit a domain-wide policy to make the Shutdown button unavailable::

1. Start the Active Directory Users and Computers snap-in. To do this, click Start, point to Programs, point to Administrative Tools, and then click Active Directory Users and Computers.
2. In the console, right-click your domain, and then click Properties.
3. Click the Group Policy tab.
4. In the Group Policy Object Links box, click the group policy for which you want to apply this setting. For example, click Default Domain Policy.
5. Click Edit.
6. Expand User Configuration, expand Administrative Templates, and then click Start Menu & Taskbar.
7. In the right pane, double-click Disable and remove the Shut Down command.
8. Click Enabled, and then click OK.
9. Quit the Group Policy editor, and then click OK.

Note: Group Policy changes are not immediately enforced. Group Policy background processing can take up to 5 minutes to be refreshed on domain controllers, and up to 120 minutes to be refreshed on client computers. To force background processing of Group Policy settings, use the Secedit.exe tool. To do this:

1. Click Start, and then click Run.
2. In the Open box, type cmd, and then click OK.
3. Type secedit /refreshpolicy user_policy, and then press ENTER.
4. Type secedit /refreshpolicy machine_policy, and then press ENTER.
5. Type exit, and then press ENTER to quit the command prompt.