Re-install windows, and when you get to the part where you tell it which drive ti install it on, go to the advanced options, and delete all the partitions. You can then go back and install windows to the un-partitioned space.
If you want to create say a 500 GB partition for Windows, you can create this partition from the advanced options, and then install windows to it, and after Windows is installed, you can go back and create another partition on the unused space.
I think you didn't format it corectly... or... all of it. right click on computer, then manage. then go to disk management. If you have something with unallocated space... that's the space you are not using. you can do whatever there. enlarge the c partition. create a new one... etc.