Casv,
If I remember correctly, the web page link will open and ask if your installation ID has six or seven digits in the first block of your installation ID . You simply select the correct answer(mine was six). It will then open a window which allows you to enter your installation ID. Once you enter, simply hit the submit button and within seconds a new page will open with your activation ID. All you have to do is just enter that number in the phone activation window of your Microsoft FSX hit next and your all done. It went pretty easy and smooth for me, just a lot of numbers to enter. If you mess it up simply call again and redo the process. You supposedly get unlimited activations with your valid product key. Let us know how it works for you...
Regards,
Bill