I've tried using multiple IE's on the same windows partition. This is helpful for many layout issues (once you apply some fixes: http://www.positioniseverythin

I've tried using multiple IE's on the same windows partition. This is helpful for many layout issues (once you apply some fixes: http://www.positioniseverything.net/articles/multiIE.html http://www.positioniseverything.net/articles/multiIE.html ) BUT, when you run multiple IE's it only uses one IE processor. For example, if you have IE7 and you want to test IE6 so you install the IE6 standalone, the IE6 standalone will use the IE7's rendering engine. This is OK in most cases, but if you want to test some tweaks that you use for IE6, you will be at a loss. For example, I wanted to use this PNG fix: http://www.twinhelix.com/css/iepngfix/demo/ http://www.twinhelix.com/css/iepngfix/demo/ which is pretty much essential for IE6 if you want PNG support -- it won't work on the IE6 standalone. I ended up not feeling that I could trust the standalone's rendering of IE6. I recommend having a dual partitioned drive with IE7 and IE6. That test machine has worked well for me as I do all my dev on OS X