Do you understand that the XP VM is in professional version because it's meant for workplaces, not to play games? 99.9% of those restrictions on direct hardware access and low 3D performance are irrelevant when your problem most likely in a workplace is for example some 16bit legacy app you need to run but can't because support for 16bit programs was dropped in Vista/7.
If you do need to play games, you can use the XP mode CD key to install XP in dual boot for real hardware access and no virtualization. Also booting the VHD image directly on bare metal from custom-made Vista/Win7 boot menu is possible under ultimate/corporate versions for the people who actually do need direct access to hardware now and then.