Microsoft has released a version of IE9 but with optimised pre-sets for Windows vista:

Overview

Windows Internet Explorer 9 has a streamlined look and many new features that speed up your web browsing experience. We give you more screen space to see your favorite sites, more than any other browser. The new tab page intelligently displays you most visited sites. A combined search and address bar means you can search and navigate from one place. With Pinned Sites, you can get to your favorite sites directly from the Windows 7 taskbar—without having to open Internet Explorer first. In addition, this product configures Windows Internet Explorer with Bing and MSN services by setting your home page to MSN, the browser’s search default to Bing, and adding a number of interesting links to the Favorites list to get you results fast when browsing the Internet. Altogether, making Internet Explorer the best way to browse your favorite sites.
System requirements

Supported operating systems: Windows Vista

•Windows Vista

•Internet Explorer 7 or later
Download:

Download: Windows Internet Explorer 9 Enhanced with Bing & MSN - Microsoft Download Center - Download Details