I use Windows Virtual PC for running some of the test VPCs and also for learning new features etc. Since I also play around with multiple versions of virtualization software (VirtBox, VMWare etc), I suddenly found that my Virtual PC directory settings were kind of screwed up (after many installs/uninstall of multiple virtualization software). So now I do not get the options to create a new virtual machine.
The good thing is that Windows Virtual PC is made up of multiple EXEs and you can manually launch then as required.
The easiest way is to directly type the command into the run bar as all of these EXEs reside in the system32 directory.
The command to launch the new virtual machine wizard is vpcwizard.exe.
You can find more about the different EXEs that ship with Windows Virtual PC on this post: Windows Virtual PC Executable