In Mac, while installing (using the Mac Installer) the first time, the "install" option will occur. But, from the next time onwards, even after removing the bundle and installing it again using the MAC installer, always "upgrade" option is displayed instead of "Install".
Reason :
MAC keeps a track of all the installed bundles in the OS under " /Library/Receipts " directory.
When we are installing the first time, Mac keeps track of the installation by updating the details under " /Library/Receipts " directory. Hence the "install" option will appear.
From the next time, although we delete the drivers from the corresponding directories, the "Install" option changes to "Upgrade".
Deleting the corresponding install entry in " /Library/Receipts " cleans up any trace of previous installation. Hence, the "install" option will appear in the installer.
It is recommended not to generally mishandle files in the " /Library/Receipts " directory.
A good link regarding this --> here
