Microsoft Windows Virtual PC

Microsoft Windows Virtual PC is a virtualisation program that is supplied built into the Professional, Ultimate and Enterprise editions of Microsoft Windows 7 and higher and available as a free download for Vista, Windows 7 and higher versions that do not have it built in.

It is slower but more flexible than VirtualBox and can even be forced to run as a software only emulator which can be handy and even though the extensions for VirtualBox are basically developed from those for Virtual PC they lack support for shared folders that VPC does support in most versions. Virtual PC is especially a better option if you are running Windows Vista or older.