I was trying to install Mac OS X Capitan on a macbookpro5,1 and during installation came across the error message:

“OS X could not be installed on your computer. No packages were eligible to install. Contact the software manufacturer for assistance or quit the installer to restart your computer and try again.”

Turns out what is causing this error are Apple’s own expired certificates. The workaround is to install Mac OS X with the computer’s clock set in the past. Follow the directions posted on Apple’s website and re-posted here:

1. Use Disk Utility.app and erase the drive you want to install OS X on.
2. Connect to a wifi network or plug in ethernet and download OS X through the App Store. Install as you normally would and arrive at failure point regarding no packages being eligible and an option to restart.
3. In the upper right hand corner of the screen, turn off wifi (top right) and, if necessary, unplug ethernet cord.
4. Go to Utilities->Terminal.app type this without quotes “date 0115124517”
5. Quit Terminal and choose the option to restart (wifi will reconnect automatically or if using ethernet go ahead and reconnect the ethernet cable.
6. The Mac OS X install should continue as expected.