You can stop or kill your program at any time using the task manager, or debugger.
You can also stop your program from within Thread Validator.
 File menu 
 Abandon Application... 
 stop the target program 
or click on the red cross icon on the session toolbar.

The target program is ended using ExitProcess() from inside the stub.
Since the session is discarded, using Thread Validator to stop the target program is usually quicker and more convenient than external stop methods.
You can easily re-launch the program again using the same settings as before.