As a convenience, I wrote a batch file that will quit XLaunchpad whenever dosbox is running (e.g., GK1, or any other dosbox-based program) and then re-launch it when you quit dosbox.

The batch file (below) needs to be run as part of a scheduled task. For instructions on making a scheduled task in Windows, see http://windows.microsoft.com/en-US/windows7/schedule-a-task.

Use the following parameters for that task:
1. GENERAL > Set it to run as the SYSTEM user (to prevent the window from popping up every time it runs)
2. TRIGGERS > Set the trigger to open when a user logs in, and to repeat every 1 minute.
3. ACTIONS > Have it start the batch file.
4. CONDITIONS > Uncheck "Start the task only if the computer is on AC power" (this only matters on laptops)
5. SETTINGS > In the "If the task is already running..." dropdown menu, choose "Do not start a new instance" (default behavior anyway)

Paste everything between the "====" below (not including that line) into Notepad and save the file as something like "KillXLaunchpadIfDosBox.bat".

====BEGIN FILE (copy below this line)====
:: Heavily based on code from stackoverflow.com/questions/162291/how-to-check-if-a-process-is-running-via-a-batch-script#_=_

:: Check if Dosbox is running; if it is, kill xlaunchpad and skip the code that would restart it
::
tasklist /FI "IMAGENAME eq dosbox.exe" 2>NUL | find /I /N "dosbox.exe">NUL
if "%ERRORLEVEL%"=="0" taskkill /f /im xlaunchpad.exe
if "%ERRORLEVEL%"=="0" GOTO EOF
if "%ERRORLEVEL%"=="128" GOTO EOF

:: Start XLaunchpad. This code will be processed only if Dosbox is not running.
::
tasklist /FI "IMAGENAME eq xlaunchpad.exe" 2>NUL | find /I /N "xlaunchpad.exe">NUL
if "%ERRORLEVEL%"=="1" start "XLaunchPad" /D"C:\Program Files (x86)\XLaunchPad\" xlaunchpad.exe start

:EOF
EXIT
====END FILE (copy above this line)====

Message me if you have any questions or run into any trouble. Good luck, and good playing!