Thanks to Sean Alexander for this:

Okay, here's my first unofficial Windows Vista "Enhancement Pack" and early feedback is that it's a good one- add 32 search providers to Microsoft Internet Explorer 7 in 32 seconds.

New in Internet Explorer 7 is a simple searchbox with the ability to search many different providers (e.g. MSN, AOL, Ebay, WSJ, Fandango) all from one place- just select the search provider (aka Scope) of your search by clicking the Magnifier glass icon and you're ready to go. The only problem is that the ability to add search providers is not in IE7 in Windows Vista Beta 1 (which I'm sure will be remedied). With this kit, you get over thirty of the top search and service providers on the Internet, including:

-Amazon.com
-AOL
-AskJeeves
-C|Net (Product search)
-C|Net News.com
-Costco
-eBay
-Encarta
-Fandango
-FedEx
-Flickr
-Google
-IMDb
-LA Times
-Lycos
-The Mercury News
-Microsoft.com
-Microsoft Help & Support Knowledgebase
-Microsoft Office Clip Art Gallery Live (Note: May require MS Office license)
-Microsoft PressPass (for the Journalists and Newshounds)
-MSDN (Developers! Developers! Developers! Developers!)
-MSN Images
-MSN Music
-MSN News
-The New York Times
-The Seattle Times
-Technorati (Blog it!)
-UPS (United Parcel Service)
-The Wall Street Journal
-The weather Channel
-Yahoo!

Download: IE7_Search_Providers.zip (4.31 KB)

How to Install:
-Select the entry you wish to add to IE and double-click it. Accept when prompted.
-To add all 32 entries at once, choose "Add All.reg"

How to Use:
-Once installed, restart IE7 (any instance will do)
-Click the Magnifier Glass icon next to Search in upper-right corner of IE7
-Choose your Search Provider

How to Change your Default Provider:
-Click the Magnifier Glass icon next to Search in upper-right corner of IE7
-Choose last option, "Search Settings"
-Change Settings

How to Remove Search Providers:
-Click the Magnifier Glass icon next to Search in upper-right corner of IE7
-Choose last option, "Search Settings"
-Change Settings

How this works:
IE7 in Windows Vista Beta 1 stores search provider information in the registry under:
HKEY_CURRENT_USER\SOFTWARE\Microsoft\Internet Explorer\SearchScopes\

If you run RegEdit.exe and do a "Find" (F3) for SearchScopes, you'll find em. Each entry has four pieces of information starting with the full Key name, for example:
[HKEY_CURRENT_USER\SOFTWARE\Microsoft\Internet Explorer\SearchScopes\CNet]
"DisplayName"="C|Net News.com"
"URL"="http://cnet.search.com/search?chkpt=astg.cnet.fd.search.cnet&q=%s&tag=srch"
"SortIndex"=dword:00000005

It's pretty easy to figure out. "%s" is the wildcard for the search string the user enters.