Correction, I was wrong, yes you can run IE 6 with IE 7, heres how:
Sure, you knew IE7 Beta 1 was up on MDSN, but you don't have a free machine to test it on. Can't install it on your main work machine, because you can't afford to mess it up... plus, you need to be testing your work against IE 6, right?
You thought about setting up a Virtual PC image, but it seemed like too much trouble for a Beta 1. Still, it would be nice to click around in it for a few minutes here and there...
Fret no more! IE has a secret standalone mode which lets you run multiple versions side by side (thanks to Joe Maddalone for figuring this out).
It's pretty simple:
Download the IE7 Beta 1 Install from MSDN
Open the install file with WinRAR (yep, it's an EXE, but it's a self extracting EXE) and extract them to a folder. Alternatively, you can just run the EXE, make a copy of the files which are extracted in the first step, and cancel the install. I was too chicken to do this on my work computer.
Look in the folder you extracted to for the file SHLWAPI.DLL. Delete this file.
Create a new text file in the folder, then rename it to IEXPLORE.exe.local.
That's it. The .local file in the folder tells the IExplore.exe instance to run in local mode, which means it won't mess with your IE6 settings, registry, etc. It sounds complicated, but it takes less than 10 minutes and it goes just great with your Friday morning coffee. Of course, you can help your friends at work (who also have MDSN subscriptions, of course) by zipping the folder and sharing it with them so they don't have to go through this crazy mumbo jumbo.