Use your debugger to debug the service while it is running. First, obtain the process identifier (PID) of the service process. After you have obtained the PID, attach to the running process. For syntax information, see the documentation included with your debugger.

Specify a debugger to use when starting a program. To do so, create a key called Image File Execution Options in the following registry location:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion

Create a subkey with the same name as your service (for example, MYSERV.EXE). To this subkey, add a value of type REG_SZ, named Debugger. Use the full path to the debugger as the string value. In the Services control panel applet, select your service, click Startup and check Allow Service to Interact with Desktop. The service must be an interactive service, or else the debugger cannot run on the default desktop. Note that this technique is no longer supported as of Windows Vista because all services are run in session that is reserved exclusively for services and does not support displaying a user interface.