There's a script called ievms that will automatically downloade those VMs and convert them for use with VirtualBox on OS X or Linux:
Turned out to be an IE7 specific regex bug (a look ahead bug), that we couldn't replicate using IE8 and IE9 set to IE7 compat mode.
Tracked down a copy of XP with IE7 and replicated the bug. Which led me to Google regex bugs related to IE7 and managed to track down the exact issue.
I can't believe that it's only raised $400 so far. It's completely excellent and I know lots of people out there depend on it.
2. Use unrar or http://wakaba.c3.cx/s/apps/unarchiver.html to unpack the segments
3. Open VMWare Fusion & choose import
4. Get coffee & wait for disk I/O
5. Install VMWare tools & pending Windows Updates
6. Take a snapshot so you can reset it after the timelimit sets in (as noted by Microsoft, they disallow storing data durably for more than 90 days)
I was a little baffled why MS would make this images only run on Windows when the people most likely to need to emulate other versions of IE / Windows would be non-Windows users.
As to why they'd use their own VM in preference to VirtualBox I don't know. But to be fair, Microsoft isn't the only company that neglects developers who aren't on their platform; "not invented here" syndrome seems to impact all software companies eventually!