Beta 1 includes a few simple enhancements to web search. Search is a critical aspect of web browsing, so we promoted web search to the top level IE frame and have included the ability to easily switch between search providers. If you are checking out the Beta 1 builds you will also see that we have included some of the top web search providers in the search box dropdown (keyboard users can use Alt+Down when focus is in the box to show this list). You can change the default search provider for IE in our new Search Settings dialog; this also changes your address bar search provider.
You may have noticed is that we do not have a way to add any new providers to this list through the user interface. This is planned for Beta 2, but for Beta 1 there is a work around if you want to add your favorite search provider to the list.
Warning: This requires editing the registry, so please proceed with caution. In order to keep your current default set of search providers, before editing the registry go into Search Settings and click the ‘OK’ button. This will copy your machine settings to your user account. This step is required due to a known bug in Beta 1. If you lose your defaults you should be able to get them back by using ‘Restore Defaults’ in the Search Settings dialog.
Here is an example of the registry entry that would add an MSDN Library search to the search box:
In the above, the key name “MSDN” can be any unique value, “DisplayName” is the text you will see in the search box and “URL” is simply the search provider’s query string. Note that the %s is where your search term will be injected into the query string.
One way to figure out how to build the search string is to type in a search term in your favorite search provider’s search box. After navigating to the results go to the address bar and see where your term is injected into the address. You can copy that entire URL into the “URL” parameter and replace the text of your query with %s as in the example above.
You may also want to read Sean Alexander’s blog post on this subject – he has created a downloadable file that allows you to quickly add 32 search providers to IE7.
When Beta 2 comes out we will have a much more intuitive way to add providers from the user interface - until then keep sending your Beta 1 feedback and have fun!
source: IE Blog