Essentially when I originally installed ubuntu, I got rid of my windows and had the hard drive reformatted. I never split up the hard drive to dual boot. Now that the hard drive is formatted for linux...how to I get some space available to be able to dual boot? It won't let me partition when I'm using the hard drive that is associated with the operating system. Please help.
Using a Virtual Machine, for example with VirtualBox, and installing Windows on it it's a good and safe alternative; if your CPU supports VT-x it should run almost fast as a real machine.
But this way you will always have to start Ubuntu before start Windows, this generally it's ok, but depends on your needings.
So if you don't want to use virtualization, you should download a "Parted Magic" ISO image, burn on a CD, and boot from this : the GParted software included will let you resize and create partitions.
You have 2 possibilities:
Method 1 is more risky. You boot from your Windows cd and install Windows on the newly created partition. Windows does not care of other oses and I don't remember if Windows will not screw up the Linux boot loader... If you can avoid Windows to touch the Linux boot loader configuration (grub) then you can later add the Windows os from Linux...