Losing memory on C drive
 

My C drive is not the main drive on my computer and it came with 15 GB but it is mainly for Windows stuff. A bunch of stuff has been installed onto the C drive but I have deleted most of it, and when everything was installed I had like 2 GB free. Now I've deleted most of the stuff on it and I have 816 MB and it keeps on losing more. It keeps telling me to do Disk Cleanup and I am but it is stopped and won't do anything. I'm running a virus scan now. What can I do

Get a new hard drive.