there are many ways of handling this.IN QTP we write the following snippet

what is your target application?

is it a web application or client server application

for a web application

1) if you want to close the web application on any defect write a code snippet some thing like this

browser( B1 ).close in side the else condition (if you are using an if else condition)

2) if you want to exit the testing Tool for any further

use Exit global iteration in the sniipet.

Press cntrl+F3

or for wrun we can kill the process by press the task mgr click on th process select the process wrun.exe and terminate it.