I bought a used iMac (mid 2011 model, quad core i5 2.7, 21 inch). I had ML on a DVD so I wanted to do a clean install. Started up from the DVD, went into Disk utility and erased the drive. Then proceeded to install. Everything seems to be going well, and the progress bar is about 80% full, but the remaining time keeps increasing (was 6 minutes left, then kept increasing up to 12 minutes, where it is now). Is this normal ? Should I just wait until the installer finishes or is something wrong. Also, there was no 'boing' sound when I started up the Mac. Obviously, as long as OS X is not installed, I can't go into the sound settings, but shouldn't it have made a startup sound ?