Speaking of Virtual PC, there's some competition out there for Microsoft.
This really isn't news, as there have always been alternatives to Virtual PC, even when it was owned by Connectix. There was SoftPC/SoftWindows and RealPC, now defunct; still in existence is the WINE Project, which is technically not an emulator; finally, still alive and well, although limited and/or difficult to use, are DOSBox and MacBOCHS, products of the open source community and Apple's open acceptance of that community.
But now there is GuestPC. Weighing in at $69, it appears to be the cheapest alternative that does not sacrifice ease of use. Compared to Virtual PC's $129 price tag, depending on how well this alternative emulator operates, it just may be a great choice.