You may install any operating system on a virtual machine using an installation ISO image. There is a number of installation ISOs available in the Public Store but you may also add any other installation ISO to your Private Library (see Add Templates).
During installation there are two drives (CD-ROMs), drive D: and drive E:. Drive D: is the image you specified as template and drive E: (WITSBITS) is where the VirtIO drivers for Windows are located. During Windows installation Windows will not find any hard drive. Click Load Driver, Browse and go to drive E: (WITSBITS), select the folder E:\WINDOWS\2008\DISK. A list with drivers will be listed. Select Red Hat VirtIO SCSI. Now the disk is found and available for partitioning. Once the operating system is installed, go to Hardware and update the driver for the unknown network interface card. Browse to E:\WINDOWS\2008\NET. In list select Red Hat VirtIO ethernet.
<note>If you power off your VM and then start it again D: and E: will not be available anymore.</note>