I have dual xenon processors with 1TB hard drive on my computer. The rest is original, with no SSDS. And yet I am still having problems installing OS X Lion on my Mac Pro 2006 1. The update for all software was ended. I downloaded OS X Lion from the app store and then installed it on my PC. When the installation is completed, the computer restarted and then the apple logo appears first on screen with a black circle started to spin. This lasted for hours before the circle stops spinning. This has gone on all night and by daybreak the situation is the same. Has this experience occurred to anyone else? Please let me know.