Add Google/Yahoo to IE7 default search

Do you know how to add Search Providers to Internet Explorer?
Add your own search provider to your copy of Internet Explorer
you have to follow steps listed in below URL:
http://www.microsoft.com/windows/ie/searchguide/en-en/default.mspx
You can set any of these as the default search provider by selecting the Make this my default search provider check box in the Add Search Provider dialog box that appears when you click the link.

Yahoo!
AOL Search
Ask.com
Bing
Google
Lycos.com