Where can I download older versions of OS X?

Guns sound great, the only reassuring sound in the game, and the moans and groans of distant and unfortunately not distant enough zombies keep up the tension. These are no ordinary plants though - they can use an array of weaponry from peashooters to cherry bombs to destroy the 26 types of zombies before they reach your front door. It looks like Left 4 Dead 2 is cementing its supremacy over the aged, lumbering Resident Evil series - these zombies are varied, fast moving and extremely vicious.

It includes general operating system fixes that enhance the stability, compatibility, and security of your Mac. No one play-through seems to be the same, making repeated play very attractive. You need to do this just once and then it just runs like a supercar every time you download a torrent.

Where can I download older versions of OS X? - They seem quite effective, though obviously it will be better with four humans. I pressed the power button to reset it, but it took me again to the same white screen, with no other option, and the process is again stuck in the middle of the line status bar.