A few people are reporting issues with this notebook and Windows 10. Try a clean install of Windows 7 or 8/8.1 temporarily and see if the device driver works. Before you do this, you can also try resetting the bios to defaults and checking for an update.

A few people are reporting issues with this notebook and Windows 10. Try a clean install of Windows 7 or 8/8.1 temporarily and see if the device driver works. Before you do this, you can also try resetting the bios to defaults and checking for an update.

Just found this link to another q550lf user, and this includes a possible fix.

http://forum.notebookreview.com/threads/asus-q550lf-nvidia-745m-not-working-i-need-help-bios-downgrade-update-needed.762464/