Tools > Options (If you don't see the Tools, Just press the left Alt. key on your keyboard).
If it still reverts, I would suspect Win 10, if you are running Win 10.

/e Once you are on the Search tab as shown in the pic, you need to select Google ( or w/e search engine you like) in the drop down box.
This post was edited by Ghot on Dec 16 2016 04:00pm