I have found articles saying this is possible, but what are the issues? Is it 'always' straightforward as shutting down your vpc and then opening it with vmware?
From this link which is nearly 3 years old it says you can but you have to copy some windows files into the vpc before shutting it down, is that still valid?
Update 1
Found this link which goes through the mouse driver issues
I'm the guy who wrote that article. I hadn't tried converting any images recently (once I moved off Virtual PC, I never looked back), but I tried again tonight to see if anything had changed. It turns out that not much has changed at all.
I grabbed a virtual disk that Microsoft published to test IE6, tried to concoct a VPC to go with it, and ended up using VMWare's converter to convert this virtual disk to a VMWare disk. It opened just fine in VMWare Server, and when I powered up, the machine discovered some new hardware devices and asked for the drivers from the XP disk, just as I'd seen before. This, I believe, is due to the emulation differences between Virtual PC and VMWare.
I haven't gone and tracked down the drivers this VM is looking for, because I don't plan to keep it around for long, but my recollection is that once these are set up, the VM will work just fine.