...snipped...If you select Start\My Computer\ then hover your mouse pointer over Local Disc (C), a que will pop up telling you how the total Gigabytes capacity is for the HD, and how many Gigabytes of free space is remaining. You will have to use math to figure the percentage of free space Vs HD space used. ...snipped...
Right-click on Local Disc (C), select properties, get a visual "pie" that shows Used Space, Free Space, and Capacity.