Why MS is distributing a time-bombed VirtualPC image???

A couple of weeks ago I was asking on our internal lists if anybody is aware of a solution to run both IE6 and IE7 on the same machine. Since, there weren't any good news about this, I was starting to look into a different direction: virtualization. I knew about the commercial product: VMWare and heard before about a similar solution from Microsoft: VirtualPC. I was very happy to hear that the VirtualPC solution is free and I jumped to try it out.
I have used for installation the copy of my personal Windows XP Professional, but because I am cleaning/reinstalling my system on regular basis - or at least I try to - and I haven't installed it correctly the first time, the second attempt have failed because of the impossibility to activate the OS. I am wondering what I will have to do when I will try to reinstall my main system. Microsoft any ideas?

I have figured out how to fix the first image I have created so for the moment I was quite happy. I don't want to enter into details, and except the fact that the audio part is not working - which for this moment doesn't really count - I was finally the owner of a VirtualPC image with my own WindowsXP Professional copy installed (even if I am afraid I cannot use my installation copy anymore).
But, after all this work I just find out that Microsoft has released a Internet Explorer 6 Application Compatibility VPC Image, which is a working WindowsXP SP2 image prepared for a possible IE7 upgrade... and I said: wow! What a nice deed from Microsoft! But then, after downloading it and reading more about it I have find out that there is a limitation: the image is time-bombed!!! I am completely puzzled why the hell would you create a time-bombed image? Is Microsoft afraid that people will start working only with VirtualPC (which works only on Windows) with this image so that they are loosing money? I must say it again: I am completely puzzled.