You know if you have Windows 10 or Windows 8.1 Pro, it comes with built in Virtualization software.
Go to Control Panel --> Programs --> Add/Remove Features --> Add "Hyper-V".
Anyway, sidetracked the main question.
Here's a video on how to dual boot Ubuntu and Windows 10.
Another way to do it is to install Ubuntu on your second hard drive while the Windows disk is unplugged.
Then when it is done, plug the Windows hard drive back in.
When the computer starts up, press "F12" to go into the Boot menu and select which hard drive you want to start up with.
Then boot into Ubuntu's hard drive and type the command "sudo update-grub2".
This will add the Windows option to the Grub Boot menu.