We can attach the debugger onto any running process at any time. Two cases:
1. Unhandled exception is thrown in some thread of a process. A dialog will pop up to ask user to terminate the process or debug it. If clicking OK, the process will be terminated; if cllicking CANCEL, the debugger specified in registry will be started up and attach onto the process and start JIT debugging.
2. At any time, we can do the attach work by two ways:
1) Run task manager -> choose one proces -> right click on it and choose "debug" -> The debugger will be started up and attach onto the process;
2) Input MSDEV -p PID in command prompt env. PID is the process id which you can gain by task manager.
And we can create dump file from user to help solving user's problem.