You are trying to install or open an app that didn't come from the Mac App Store but you got a message saying App can't be opened because it is from an unidentified developer. This is how you bypass it.
Mac OS X 10.8 Mountain Lion is out and ready for download. If you are willing to invest $20 and an hour of your time to upgrade you Mac computer, you won't be sorry.
If you want to make a clean install of the new OS X Mavericks or even the older versions of Mac OS X, than I strongly suggest you to create a bootable OS X key or a drive.
VirtualBox is a great free cross-platform virtualization program that enables you to run Windows, Linux, Mac OS X and other operating systems on you Windows, OS X or Linux computer.
If you experience an Mac OS X program to freeze and you cannot exit it by clicking quit or using a keyboard shortcut, you can always force it to quit using the Activity Monitor.
If you are the kind of person you want to read what has been changed before updating an app you can disable the auto app update setting. Or enable if you want updates fully automated.
