Look into...

You may need to do a "repair mode" option of your OS. I have no idea what your PC is or OS, etc.. In most cases if you have the OS disc, iy should contain the repair option within a menu once booted from it. You may want to check your PC maker's support website for details, but proceed once you know what needs to be done. There are also "repair disc" made for Windoze of your OS than can be had legal and proper from online sources. Google for such, get the .ISO file and burn and check results.

I suspose the Fn-F7 is the brightness up/down of the display. If that doesn't work, then the repair option is a possible fix. The other fix, is using a "restore point" finding a date that was before all of this started or seemed to. If you haven't already use your anti-virus pgm. and run it after updating it to do the best it can. I hope all this helps but next time post all details.

tada -----Willy happy