I collected over the years from the various Macs that I owned the OS X installers for versions 10.6 through 10.11. However, when I tried to use the OS X 10.7 installer on an older MacBook with 10.6 (to make it "iCloud ready") I got an error message, saying that this installer was too old (or something similar) - and I could not use it. I then faintly remember that I read some time ago that Apple "disabled" all (or some?) installers from some (or all?) OS X versions and replaced them with newer versions. Is there any way to know which installers work or not work without actually trying to install these versions? Is there a way to get new installers without having to buy them new? When did Apple start to offer OS X versions for free? Thanks for your help! --- Post Merged, May 2, 2016 --- I just found the article about here on MacRumors about the expired Developer Certificate (http://www.macrumors.com/2016/03/03/older-os-x-installers-broken-by-certificate/). This means there seems to be a "remedy" to still use the old installers. Did anybody try this and can confirm that it works? (I will try certainly myself tomorrow.) I then also found all OS X versions from OS X 10.8 Mountain Lion in the Purchased section of App Store on my Mac - but I cannot re-download them (except for OS X 10.11). Is there a trick to download them again?