I've been using IETester for years but today I stumbled upon another browser package called BrowserSeal.BrowserPack that not only includes IE5.5/6/7/8, but also IE 1/2/3/4, Opera 8/9/10, Firefox 3/3.5 and Safari 3/4. Not a bad effort! Unlike IETester which executes all the browsers in a single tabbed window, BrowserSeal.BrowserPack is really just a collection of portable browser versions, so you are left running 10 windows instead of one. What I suggest is not installing the IE browsers in BrowserSeal.BrowserPack and continue using IETester instead.

PS: And if you want to run Firebug in your 10 new browsers you can bookmark the Firebug Lite bookmarklet and you get almost the same featureset as the native firefox extension gives you!