The search bar is now part of the URL address bar. Essentially, the URL bar and the search box are combined into one in IE9. To learn more about the IE9 search bar go here:
http://www.gotknowhow.com/articles/search-in-inter...
If you want a separate search bar for Internet Explorer 9, you can download the Google Toolbar or Bing Toolbar:
Google Toolbar:
http://www.google.com/toolbar/ie/index.html
Bing Toolbar:
http://toolbar.discoverbing.com/toolbar/en-us.html
Yahoo Toolbar:
http://us.toolbar.yahoo.com/