It's free and open source!

It offers a free alternative to VMware. The license costs for VMware are quite large if you are running a big cluster. OpenStack on the other hand is free, open sourced solution. Of course there are some costs; hardware, electricity, administration, OS licence if you decide to run it on RHEL.

I started to follow this guide http://networkstatic.net/building-a-windows-image-for-openstack/ since it felt like the best one found from the Google.