This is a bit long winded, for which I apologies, but I want to make sure I've included all details. Bit of background: I need to reinstall the original OS that came installed on my Mac Mini because the Apple Store app has been deleted and without it I cannot get Software Updates: the Apple Store app is an integral part of the OS and cannot be downloaded separately. The previous owner upgraded to Mountain Lion under their Apple ID so I cannot reinstall from the recovery HD as my Apple ID doesn't match the installed OS. I have been advised to completely erase the Mac using the Disk Utility in OS X Recovery which will install the factory installed OS (Lion) without the need for an Apple ID. Once Lion is installed I will then buy/install my own copy of Mountain Lion under my own Apple ID (I don't want Mavericks as there is conflict with some Adobe CS5 apps that I need). So, I attempted to perform the erase: option-r on restart > Disc Utility > highlight the Toshiba HD showing top left of the window's side bar > click the erase tab > choose Mac OS Extended Journalled > choose a name (I chose Macintosh HD) then choose the number of security overwrite passes. When I press the 'erase' button I get the following window/message: 'Secure Disc Erase failed. Secure Disc Erase failed with error: couldn't unmount disc'. So I tried again, but by mistake clicked on the Macintosh HD in the left hand side window of Disc Utilities rather than the Toshiba drive shown above it. As a result, I think I've erased the recovery partition (previously it showed as 10.8.2). Now, when I restart the Mac normally without any keys pressed at start up, I don't see my desktop/files/apps etc. (presumably because i've deleted the Macintosh HD) but get the OSX Utilities window showing the following options: Restore from time machine back up. Reinstall OS X (which I cannot do as the copy of OS X Mountain Lion is linked to the previous owner's Apple ID). Get help online. Disc Utility. How can I get back to OS X Lion (the OS that was originally factory installed on this Mac) so I can then buy/upgrade to Mountain Lion?