[CentOS-virt] What are these directories on virtio-win-0.1-81.iso?

Hi All

I just downloaded virtio-win-0.1-81.iso from

     http://www.linux-kvm.org/page/WindowsGuestDrivers/Download_Drivers

Looking through the ISO, I find two directories: WLH and WNET.
What are they?

Also, I find a WXP and and XP directory.  Why two of them?

Many thanks,
-T