On step number 5, I find the download an open it and it says "The following disk images could not be opened "InstallMacOSX.dmg" (not .pkg reason) "image not recognised" ***? how do I get it recognised? I have a 2009 Macbook and need to upgrade to 10.11.4 for medical device upgrades but am struggling to get the computer to help me, to the point of wanting to throw it.
How do I upgrade from OS 10.10.5 to 10.11.4? without loosing sleep or wanting to kill something?