If you want to run the Windows 8 Beta on RHEL 6 you need the `virtio-win` package installed. You can get it by subscribing to the “Supplementary” RHN channel.
Silly me. I thought I could just download the Windows 8 Beta and install it on a virtual machine with RHEL 6. Instead I kept getting an error message about a missing DVD driver. Since I wasn’t sure if this was a Windows problem or a `virt-manager` problem I filed bug #809160. From that I learned about virtio-win.
Install `virtio-win` and restart `virt-manager` and everything should work as expected. Note, you must be subscribed to the `supplementary` RHN channel where this package is located.
$ su -c 'yum install virtio-win'
I believe that you need similar packages for Fedora, though I am not sure if they are provided by yum or what you have to do. Has anyone installed the Windows 8 Beta on Fedora and if so, did you have to do anything special with `virt-manager` to make it work?