How to abort a render?

[cgirerd]

I rarely add shadows to a render, but I decided to do it today, got the picture I wanted then I went to change something and the render started to redraw - and of course with shadows it takes forever. I tried all the key combos I could think of, tried to close the window - nothing would stop the dang thing. I finally ctrl-alt-deleted Chief to stop it so I could do something else. I'm sure there must be some way to stop it that I'm missing... I checked old threads and the manual and couldn't find anything where I looked...

Any ideas?

Thanks,
Christina