256986 (http://support.microsoft.com/kb/256986/EN-US/) Description of the Microsoft Windows Registry

Debugging a Windows NT service can be done in several ways. You can debug aservice while it is running by attaching to the process ID of the Servicethrough a debugger such as NTSD or WINDBG. You can also set Windows NT sothat it will start the process in a debugger when you start the service.

These techniques are useful for different debug scenarios. This articlediscusses the steps that you need to take when you want to debug a serviceduring the initialization.

WARNING: If you use Registry Editor incorrectly, you may cause serious problems that may require you to reinstall your operating system. Microsoft cannot guarantee that you can solve problems that result from using Registry Editor incorrectly. Use Registry Editor at your own risk.

In order to set up Windows NT so that it will start the Service in adebugger, the following registry key needs to be set during the Serviceinitialization:

1.	Start Registry Editor and locate the following Registry subkey in the HKEY_LOCAL_MACHINE subtree: SOFTWARE\Microsoft\Windows NT\CurrentVersion\Image File Execution Options
2.	Create a subkey with the name of your Service executable (for example, Myservice.exe)
3.	To this subkey, add the REG_SZ value called Debugger and the full path to the debugger you want to use, but omit the ".exe" extension. You can add any command-line option for the debugger as well.
4.	Close Registry Editor.
5.	Start the Service. NOTE: The service must run as Local System and have "Interact with Desktop" enabled in order for the debugger to show up on the default desktop.For example: HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Image File Execution Options\yourapp.exe "Debugger"="C:\windbg -g"

The debugger will start when the image for the Service executable is loadedinto memory.

For additional information about Windows NT debuggers, click the article number below to view the article in the Microsoft Knowledge Base: