[Users] Adding a Second disk to a virtual windows 2008 R2 server

Hello, What is the way to go to add a second disk to my virtual windows server 2008R2 ? I'm using ovirt 3.3.3 on a centos 6.5 server. The windows server is in use so I 'm not at liberty to reïnstall a new one without loosing a lot of time. Kind regards.