Help! MacBook won't boot up after security update

I think I am royally screwed this time. I just got the prompt to update with new security software so I accepted and now the thing wont' boot up.

I am stuck at the apple logo and spinning wheel. It seems to be stuck forever. Is there a way I can retrieve my files at least ? I don't mind reinstalling everything but I need my important files back. Help!

I'm assuming you don't have a backup? Try booting your Mac up in SAFE mode and see if you can access anything that way. When you hear the POST chime, press and hold the shift key until you see the spinning circle.

Also, have you tried to reboot the machine from a cold start to see if it boots that way?