Formatting Windows is generally easy because most computers have only one harddisk. If you try to format on the computer which has two harddisks, you might experience an error like this:
Setup was unable to create a new system partition or locate an existing system partition. See the Setup log files for more information.
To manage this problem, you should unplug one of your harddisks. Probably one of your harddisks is SSD. You should unplug that. After you install Windows, you can plug in it again.