Parallels and Virtual PC for Mac

There’s a ton of information out there about installing Windows on an Intel-based Mac using Parallels Desktop for Mac. Essentially, one loads Parallels on one’s computer, follows the instructions via PDF et voila, Windows on your Mac while you’re running OS X.
There’s very little information out there (actually, none) about what one should do if one has invested previously in Microsoft’s now-unsupported Virtual PC for Mac. A few years ago, I bought Virtual PC so that I could be sure that the sites I was creating looked and worked well on 90% of computers (e.g. Windows). It was a necessary investment.
It turns out that Microsoft, in its semi-finite vision, bundled the Virtual PC application with Windows XP Professional. There’s no way to unbundle them; they live together on a few, unusable, CDs in my office cabinet. I found an old Windows XP install disk to try to load with Parallels and it worked. Except, when I re-booted XP and was asked for my Product Key, the key from my old (legitimate) Virtual PC disk was useless or, at least, not recognized by the new XP just loaded. Microsoft gave me a way to purchase a new key, for USD 200.00, but I already own a valid copy of Windows XP and I don’t want to pay an additional $200.00 for XP. I’m going to call my friends at Microsoft and I’ll see what they can do for me.
Postscript (10/31/06): It turns out that you cannot upgrade from Virtual PC for Mac to a plain old, vanilla version of Windows XP Pro. I spent 45 minutes on the phone with three different Microsoft tech/sales folks, and, alas, that’s the story. For those of you with Virtual PC for Mac and who are now going to use Parallels with Windows XP, you’ll have to buy a new version of XP, straight out. While I understand Microsoft wanting to make money on a newer operating system, the company really should have an upgrade path for semi-dedicated Mac users who are committed to ensuring that Windows, well, works.