No you can't install windows (any kind) onto a Ubuntu drive. Windows 8.1.1 and Ubuntu are incompatible in their file structure.
You could purchase a new (or blank out an old) hdd then install windows on that… temp disconnect the other hdd's during this install so that the current 7-U file structure isn't changed.
The advantage is that the system will run at full power without getting funnelled into a virtual interface so you see how well your motherboard, cpu and ram performs.
The disadvantage is the cost of the extra hdd and of course there is a risk that you might corrupt the current system files if you forget or incorrectly set them.
Another option is to install 8 as the main system then place 7 and Ubuntu on as...