Many users want to switch to Free operating systems but have one or two critical niche programs for which they are unwilling or unable to use any of the available Free Software.
With proper use of Xen's new HVM support on modern CPUs it should be possible to provide these users with the ability to run a non-Free guest.
- The main goal would be the ability to easily set up an `empty' guest and allow the user to install the guest operating system.
- Sometimes the reason for the use of Windows is a program that wants to talk to specific hardware, nowadays often via USB. So a USB relay between Xen guest and the host USB would be very helpful.
- Graphics performance is not ideal when the guest is displaying to emulated VGA hardware. With suitable insanity it might be possible to share the video card between Windows and Linux by having each of them putting the card into a sane text mode before switching display, so that they know to reinitialise the card into their graphics mode. Due to the fact that the video card does DMA this will probably break the security encapsulation but it's not likely to cause hopeless unreliability. This approach is unlikely to work to support games.
- Popular non-free operating systems gradually rot after installation. Xen could be used to prevent this: at the end of each day, the changes to the guest's disk are just thrown away. The user would preserve their files on (say) an SMB volume.