Just left the Genius Bar where they installed Snow Leopard on a 2008 MacBookPro successfully. Have a bad disk drive so they installed via an external drive. Install was successful after about 45 minutes. Computer restarted fine in 10.6. We left and brought machine home. Now, on start-up, the grey apple shows on-screen with spinning gear then apple turn to a circle with line thru it and gear continues to spin. What the ****? Of course, Apple Care is closed for the night and leaving town in 48 hours. Ugh...help!!!!!