If you have a raw DMG file:
(4 GB recommended).
Apple maintains hidden support pages for older installers. For Mountain Lion, the official recovery link is: download mac os x mountain lion dmg
To help you get started with your installation, would you like: to create a bootable USB? Steps to troubleshoot common "Certificate Expired" errors? Guides for installing Mountain Lion on a Virtual Machine? If you have a raw DMG file: (4 GB recommended)
For those who cannot access the official store, the Internet Archive (archive.org) is the most trustworthy repository for vintage software. Search for "Mac OS X 10.8 Mountain Lion" on the Archive to find user-uploaded disk images. This is often the most reliable way to get a raw DMG file suitable for emulation (like QEMU or VirtualBox) or burning to media. Steps to troubleshoot common "Certificate Expired" errors
| Problem | Solution | |---------|----------| | “This copy of the Install OS X Mountain Lion application is damaged and cannot be used to install OS X.” | The date on your Mac is likely wrong. Set the date to 2012–2014 manually via Terminal: date 0101010113 (Jan 1, 2013). | | DMG won’t mount – “invalid checksum” | Redownload from a trusted source. File corruption is common. | | Mac says “This version of OS X 10.8 cannot be installed on this computer” | Your Mac is too new (post-2014) or too old (pre-2007). | | App Store missing “Purchased” copy | Sign in with every older Apple ID you’ve ever used. Some users have success by viewing “Hidden Purchases.” | | Internet Recovery installs Lion, not Mountain Lion | That’s fine. Install Lion first, then upgrade to Mountain Lion via a DMG. |