We have Surface Pro 3 tablet with a 256 GIg Hard drive. It runs W8.1 64 bit, 8 gigs memory and Office 2013. This 256 Gig hard drive is reporting that its almost out of space. Program and user files included, it should be showing over 100 gigs of free space. Yet it reports it has only 500 megabytes left. What could be causing this?