Hello Woodlands,
What probably took place is your computer was upgraded and the entries in program files stayed orphan. The new driver downloaded from Windows Update cannot remove them after the fact, because it can't access it (access rights).
You would not be able to run 7.9.1488.0 on Windows 10 v1607 unless you specifically added it manually as it was removed during the update from v1511 to v1607. However, the Windows update process is not 100% and might have not removed all traces (and only deactivated the older driver).
If you wish, you can
use our End User Cleaner to remove the 7.9 traces and then reinstall 8.0 from zero. However, if the installer says you are running 8.0, your computer is running 8.0.
Kind regards,
Alban