On my Windows machine -- I typically test different versions of Internet Explorer using an array of Virtual Machine instances (which obviously requires a fair amount of investment in time and money). In a pinch I have also used IETester -- which at times can be a little unreliable.
However, I just discovered IE Collection and was wondering if people have used it -- and can I rely on it for web page testing purposes?
Would love to know what you think.
Yes, it is reliable for checking your sties as to how they appear in different versions of IE but i suspect you will be interested in IE starting from 5.5 onwards. You should use that if you want to make sure that your site looks fine even in damn IE.
No, I would not rely on it - at least not completely (i.e. use it just for quick IE tests, but still retest everything later in a reliable solution).
There are differences when testing both with IETester and IECollection, most notably in Javascript processing.
See a similar thread here: http://superuser.com/questions/118069/whats-the-easiest-way-to-install-multiple-versions-of-ie-and-firefox-on-the-same/
From the few answers there, the most viable solutions are virtual machines (which you are using already), or web services which do the testing for you (although these might not be suitable for everyone, i.e. due to data confidentiality).
IE isn't designed to be installed side-by-side with other versions. Most of these "all-in-one" testing tools use a trick of the Windows loader that lets you override system DLLs with DLLs in a local directory. Then they package up a random subset of Windows DLLs from different operating system versions and different IE versions and drop them into some UI. The fact that they happen to seem to work in this manner is a coincidence and not reliable. There will be errors and other strangeness, and probably crashes if your target operating system is far enough from the IE version (e.g. IE6 on Win7) and your webpage is significantly complex.
So, to be clear, no, don't use these tools because you can't rely on them to give you an accurate result. If you want to know how your page looks in a given IE version, use the IE App Compat VHDs available free from Microsoft here.