Multiple Internet Explorer® versions on one computer
Yes it is possible.
Via Simon Willison, WaSP and various others comes the breaking news that it is possible to install multiple versions of Internet Explorer on a single installation of Microsoft Windows (despite Microsoft's protestations that it is impossible due to IE being too tightly integrated into Windows).
Downloads of modified IE5.01 and IE5.5 installs have now been created by Ryan Parman. Furthermore, Luke Redpath has created a nice set of colour-coded icons so that you can tell your IE versions apart.
The advantages this new information will bring to Web Developers are not to be underestimated. Before this, you either needed a computer for each version of IE you needed to test, multiple operating system installs on a computer or a copy of VMWare or Virtual PC (neither of which is free and both of which are quite slow).
Certainly, as far as I'm concerned, this will assist browser compatibility checking for Voidwars (most of the time we just don't bother to check IE5.x at the moment). I just wish we'd known about this 3 years ago when I was working on a totally IE-centric intranet at Tyco Electronics.
Let's hope someone figures out IE4 soon…
(Interestingly, as I was searching for a link for "Virtual PC" I noticed that Microsoft has now acquired Connectix and are now developing their own version of Virtual PC.)