Actually if that's a win7 VM you are doing it's nothing to do with being a VM but rather that the updates process is semi broken from a clean SP1 install.
There's so many updates it basically can't handle it.
There was a good rant about it along with some workarounds like the rollup package and wsusoffline to mitigate this in /r/sysadmin last month
And on a semi related note for future reference for people looking for the windows virtio drivers the official home from a fedora perspective is here:
There's even a yum repo to make it easier to keep up to date on them.
Although the ISO doesn't include the spice agent installer to handle automatic resizing of the resolution when changing the window and clipboard sharing... But it does link to the location for the installer for that