Just in case you didn't know already, testing websites in Internet Explorer is annoying, especially given that you can't have IE6 and IE7 installed simultaneously. Enter a free tool from Microsoft: Microsoft Virtual PC. This program is a decent VMWare like setup, but it gets better because Microsoft has actually released images for you to use with them. You can find images with IE6, IE7, and even IE8 beta all on their download page.
I know, a free tool from Microsoft that makes your life a little easier. It's weird!