Beware, Windows 8.1 is not compatible with all computers that have Windows 8. I learned the hard way. I have a Lenovo G780, I upgraded to Windows 8.1 (had Windows 8-so it was free), after all said and done WiFi would not work. Spent many hours trying to get it fixed, install, reinstall drivers, many supposedly solutions found on internet, I tried them all.
So I ended up doing a refresh to revert back to Windows 8, now have to reinstall most of the programs. I would recommend checking compatibility at the MS Compatibility Center.
HERE