Hello Jcbaldwi, and welcome to Seven Forums.
Could you post a screenshot
of your Disk Management (diskmgmt.msc) window showing your C: drive's layout to see if there may be unallocated space on it.
In addtition, this may be able to help to find what is using your HDD's space. Be sure to see the NOTE box at the top of the tutorial below.
Hard Disk Space - Free Up and Recover
Hope this helps for now,