Under Personal, select Security & Privacy. Please follow this procedure to correct the problem: The Apple certificate tells MacOS 10.7.5 and 10.8 it is compatible with that software. Also, Apple recently released an update to 10.7.5 that included this Gatekeeper feature. Since the Backup Plus line of drives and its software was released in the first part of July 2012 and 10.8 was not released until later in that same month, the software that was included with the drive did not have that certificate written into it. The version of the NTFS driver that was originally included with Seagate Backup Plus drives does not have that 'Apple Certificate'.

Gatekeeper can be configured to block the installation of any software that does not have an 'Apple Certificate' written into it. This is because MacOS 10.7.5 and 10.8 include a new feature called “Gatekeeper”.

When installing the Seagate NTFS driver in MacOS 10.7.5 or 10.8 (Mountain Lion), you may discover that MacOS is blocking the installation. Troubleshooting information in case MacOS 10.7.5's and 10.8's 'Gatekeeper' software prevents the installation of the Backup Plus or GoFlex NTFS driver.

How to upgrade mac 10.7.5