Changing your Internet Explorer Search Button back to it's default can be done in less than 5 seconds.

Simply click on this link: Restore IE Search Button

(Note: A Save As Box will appear, select Open this File from it's Current Location)

Click ok and a New Box will open saying are you sure you would like to add the information. Click, Yes and then OK and your IE Search Button will be restore.

OR

Manually: Just click on the Customize Button on the left side of your screen, select, use one Search Service and choose the search engine of that you prefer.