So I did something really stupid and now my mac book pro won't start up - it just goes to a blue screen with a spinning wheel. Basically, I tried to get rid of the region lock on my laptop using this firmware: http://forum.rpc1.org/viewtopic.php?f=30&t=46116 It didn't work so I changed my OS X software version number (which is originally 10.5.8) to 10.4.9 by modifying the code in file /System/Library/CoreServices/SystemVersion.plist using Terminal. After restarting, laptop won't start up. Please help!! * Tried NVRAM reset, tried to load as Windows, tried to load in safe mode - nothing works..except single-user mode.