Sometimes bing can be really annoying... Here's what you can do:
First go to Internet Options and click on Advanced
Then click Restore Advanced Settings and then click Reset
Check the box that says Delete personal settings (don't worry you'll get them back) and then hit reset.
After that is done close out of your browser and open it again.
You should get the standard Welcome to Internet Explorer Pop-Up
Click don't use recommended settings and then next.
Then hit Choose my settings and then finish
Now go to google.com and you should see something on the top of google that says: Get to google faster. Update to your default search engine.
Click sure and when you get the pop-up check the box that says make this search engine my default search engine and hit Add
Now just to be sure go to Manage Add-Ons and check the Search Engines section and make sure Google.com is set as default.
Now if you restart your browser completely you should get Google.com the default search engine.
Hope this helps!