iMac slowed down the other day, struggling with iTunes, so rebooted in safe mode, but the progress bar won't go past, maybe 2%. I've left it for three hours with nothing. I've tried cmd-opt-p-r, shift, opt on its own, and every other suggestion I can find, including disconnecting mouse and keyboard, and the result is the same. Any other suggestions? Help would be very much appreciated. Computer is about 8 years old, and nothing has been added in terms of memory etc. Was about to update the software (a bit late) so was about to back everything up. Anyway, thanks in advance.