How to install IE 7 and keep IE 6

As every web developer knows (or should know), testing your work across all major web browsers is part of doing business. My own setup is primarily on OS X using Safari and Firefox, but I also keep Parallels open running Windows XP and IE 6 to quickly catch problems.

But there's one browser missing -- IE 7. Yeah, it's supposed to be much more in-tune with the rest of the browser world when it comes to supporting web standards, but it's still lagging behind and buggy. Up until Vista was released I could pretty well ignore IE 7, but those days are gone.

So...just install IE 7 in XP and everything will be fine, right? Wrong. Installing IE 7 deletes IE 6, which is still the dominant Windows browser to test against. I could install a second build of XP as a separate virtual machine in Parallels, but thanks to Microsoft's draconian activation scheme, that won't work. Buy Vista? I could, but come on. Plunk down nearly two hundred bucks just to use IE 7? There has to be a better way.

Thankfully, there is. Like the old days of evolt.org's browser archive, enterprising developers have built a standalone installer for old versions of IE. Here's how it works -- you install IE 7 through Windows Update, which will remove IE 6 from XP. You then download and run the aforementioned installer, and choose what version of IE you want to bring back to life -- IE 6, IE 5.5, IE 5 and/or IE 4. I went ahead and installed them all.

The result? Five flavors of IE in XP, each running side by side without any code overlap or problems so far as I can see.

Update: Looks like you can use the same XP license with more than one virtual machine in Parallels, though you may be breaking the license agreement (of XP) in doing so. Anyway, all you need to do is clone your existing XP virtual machine, startup the duplicate, and update it with IE 7. Personally, I'd rather keep just one virtual machine running, and not risk the chance of Microsoft crippling / de-authenticating XP, but the clone option seems to work well for some.