Get your Windows iso and a virtio drivers iso and store them inside the global zone. The virtio drivers will be needed for Windows to recognize the disks during install.
The virtio drivers can be downloaded from https://fedorapeople.org/groups/virt/virtio-win/direct-downloads/stable-virtio/
> ls /rpool/iso
windows_install.iso
The HP Microserver Gen8 when configured to disable RAID on the front loading bays (something you should do if planning on using ZFS) is unable to boot from the 5th SATA port, which is usually reserved for the front optical drive.
There are several workarounds, but the most popular one is installing a separate bootloader on an USB drive or MicroSD card, and from there load your OS of choice.
Grab your USB drive, create a MBR partition table and a FAT32 partition, and mark it