First post (sorry for its length), but I'm a long-time lurker. And I'm stumped . Please help! The computer is a MacBook Pro Unibody, i5, early 2011, 4GB RAM, Intel HD3000 Graphics. Original OS - Snow Leopard. I 'upgraded' the OS to Mountain Lion and all was fine for 7 days, until the screen remained black on booting up (not completely black - there was a minor 'brightening' when I adjusted the screen brightness, F2, on booting). Nothing when the PRAM and SMC were re-set. Nothing when I attached an external monitor. Could not boot to Single User Mode or to Open Firmware, either internal or external screen. Could not boot to SL DVD either internal or external screen. COULD boot from an external drive with SL OSX installed, connected through USB to Unibody, but only external monitor working (quality of display - Dell S2240L - defaults to 640x480 and can only be re-set to a maximum of 1024x768 and very poor at that! Distorted.) I removed the HDD and could boot my iMac from it, when it was attached through the iMac's USB port. The Unibody screen was swapped into a friend's laptop and there is nothing wrong with the screen. The screen was put back into my Unibody. The video chip solder joints on my Unibody were heated with a heat gun; maybe there were some dry-solder joints? After each of the following procedures, the firmware on the Unibody was re-set. I don't know what I did this, but an HDD with Windows 7 installed was swapped into the Unibody. Windows loaded (on the Unibody screen) fine, right up until it crashed out towards the end of the boot process (hardware conflicts?), but the screen and, presumably video chip, is therefore confirmed working? I re-seated the Unibody HDD, booted from the external drive (OS SL, as above) through the USB port, re-partitioned the drive and installed SL onto the Unibody HDD from a retail SL DVD, everything watched through the external monitor. I did not sign up to my Apple account during the registration process. The external drive was then disconnected. Re-booted the Unibody after this install (to the external monitor) and, getting stir-crazy by this time, applied updates to SL, thinking that maybe some firmware updates might come down and solve the problem. At the end of that process, SL had been magically updated to Lion (10.7.5) - what is that all about? And still nothing on the internal monitor. As a final shot, I left the Unibody turned off for a couple of hours, re-booted and nothing. I removed the external monitor adapter for a couple of seconds, re-connected it and, voila, the computer booted (but only to the external monitor). So I have registered here to seek some sort of help with this problem. My head hurts. Any ideas, advice or comments, please?