How to Turn off preview while rendering?

Simply close the composition viewer before rendering. You may also use Caps-Lock to suppress screen redraw, but if you want to keep working oin your PC, that becomes impractical. Also note, that no redraw will happen, if you simply minimize to the task bar. It's not as efficient as the other two methods, as AE still populates the buffer even if it isn't visible, but should be good enough. And don't be fooled: If your system won't render the frames due to memory errors, turning off the refresh won't save your behind, either. The result buffer is only a few MB and the other memory costly operations still happen in the background in the program's invisible memory caches.

Mylenium