Windows Virtual PC is unable to host a virtualized install of Windows 8. Windows Virtual PC is being depreciated in favor of Hyper-V.
Steven Sinofsky, head of Windows, wrote a blog post titled Running Windows 8 Developer Preview in a virtual environment where he goes into the subject in detail. It's a good read. Halfway down he says:
"... our baseline assessment is as follows:
- Hyper-V in Windows 8 Developer Preview
- Hyper-V in Windows Server 2008 R2
- VMware Workstation 8.0 for Windows
- VirtualBox 4.1.2 for Windows
- Microsoft Virtual PC (all versions)
- Microsoft Virtual Server (all versions)
- Windows 7 XP Mode
- VMWare Workstation 7.x or older"
So no, Microsoft Virtual PC does not official support Windows 8. If an unofficial hack comes out and gets it running it will almost certainly be a sub-par experience.
The new official virtualization solution from Microsoft is Hyper-V and it will be available not only on the server but also on the desktop.