It's called, "Add to Search Bar 1.8."
Once installed, you can then add any search engine to the upper right search bar in Firefox. Simply visit the search engine's site, place your mouse in the main search bar area, right click and select, "Add to Search Bar..." The Search Engine will then be added to Firefox's search bar!
This Add-on works for both Firefox in Windows and Linux. So, if you run Windows, make the switch to Firefox. It's more secure and customizable than IE. Then just do yourself a favor and make the switch to Linux. Firefox is the main web browser and, running in Linux, you'll have a safer, more secure internet and computing experience with no threats from Windows viruses and Trojans.