Actually Internet Explorer 9 beta runs on Vista as well as Windows 7 (32bit and/or 64bit). If you decide to use the IE9 beta beware that it can cause printer issues. I had to rollback to IE8 on my 32bit Vista, 32bit Windows 7 and 64bit Windows 7 machines and reinstall my printer drivers to regain the ability to print. It is very possible that the latest beta may have corrected this problem but I don't want to give it a try.

The SVG support in IE9 was not very impressive in the original beta.