Disabling Windows 2003/2008 "reason for shutdown" dialog

1. If your computer is

   a). member of a workgroup, then run gpedit.msc. This opens Local Group Policy Editor.

   b). member of a domain, then create and link a Group Policy Object (GPO) and edit this GPO.

2. In policy editor navigate to

   Computer Configuration
   Administrative Templates
   System
   

3. Double click: "Display Shutdown Event Tracker" Set it to disabled.

4. If it was GPO, refresh the policy with gpupdate /force

[Source]

Open gpedit.msc > Computer Configuration > Administrative Templates > System

click Display Shutdown Event Tracker and then disable

You can use following details to change or disable shutdown event log:

1. Start Registry Editor.
2. Locate and then click the following registry key: HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\Reliability\UserDefined
3. On the Edit menu, click New, and then click Multi-String Value. This creates the new key and gives it the temporary name "New Value."
4. Type the name of the registry key in the following format, and then press ENTER: UI_control_flags;major_reason_number;minor_reason_number The UI_control_flags section of the value name can contain one or more of the following values:
   • P (Indicates that the reason is planned. If this value is omitted, the default is unplanned.)
   • C or B (Indicates that a comment is required.)
   • S (Indicates that the reason should be displayed in the user-initiated shutdown dialog box.)
   • D (Indicates that the reason should be displayed in the sudden shutdown dialog box.) For example, if you want a reason to be displayed in the sudden shutdown dialog box, the shutdown is unplanned, and the shutdown corresponds to a major reason 2 and to a minor reason 2, type the following value name: D;2;2
5. Double-click the new key, and then define the value data in the following format: Title

Description Each value is made up of two strings on separate lines; the first string is the title (this is displayed in the list) and the second string is the description (this is the text that is displayed following the selected reason).

For example, if you want to create a custom reason for a natural disaster, you can define the value data as follows: Natural Disaster (unplanned)

A flood, an earthquake, a tornado, or another unplanned natural event requires that the computer be shut down. Specify the natural event in the comment area. - Quit Registry Editor.

Notes

• You can specify both S and D for UI_control_flags, but you must specify at least one of them for the parameters to be valid.
• If the UI_control_flags section contains any characters other than the characters that are listed in the "Custom Options for Identifying a Shutdown Cause" section of this article, or if the UI_control_flags section exceeds five characters, the message is not valid and is not displayed in the user interface. You can specify that the characters appear in any order.
• The major_reason_number is a number from 0 through 255. If this section is left blank, if it contains a number that is not in the valid range, or if it contains a number that is not an integer, the message is not valid and is not displayed in the user interface.
• The minor_reason_number is a number from 0 through 65,536. If this section is left blank, if it contains a number that is not in the valid range, or if it contains a number that is not an integer, the message is not valid and is not displayed in the user interface.
• The custom reasons are sorted in the user interface by two keys in the following order: MajorReasonNumber, MinorReasonNumber.
• The maximum length for the title is 64 characters, and the maximum length for the description is 96 characters.
• If you set the following registry key to any non-zero value, and you have correctly defined at least one custom reason, the standard Windows reasons are not displayed in the Shut Down Windows dialog box: HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Reliability\ShutdownIgnorePredefinedReasons