C-drive keeps filling up

Here's a problem that I haven't been able to resolve for the last two months.  I've researched this problem on this forum and nothing been able to solve it yet.  My work computer's c-drive keeps filling up to capacity.  I have a 235 GB hard drive with very few programs loaded onto it and almost no picture or video files taking up space.  The computer is hooked up to a network here where I work, but nobody else has this problem.  Even if I'm able to free up several GB's of space, the c-drive will fill up in just a couple of days.  I think I might have a virus.  These are the measures I've tried to correct this issue:

• Ran Disk Cleanup which freed up about 2 GB's initially.  After a couple of days, the c-drive filled back up again.  Subsequently, running Disk Cleanup only free's up a few MB's now.
• Ran MalewareBytes, Eset online scanner, and Super-AntiSpyware programs to try to identify a virus, but neither of them can find anything other than cookies.  I've also run these programs in Safe Mode.
• My Microsoft Security Essentials program had been removed, and I can't get it to re-install.  I even tried several work-arounds listed on this forum to install it, but I still get error messages when installing.
• Tried the "Fix It" function
• Tried System Restore but apparently that's been disabled too since there are no restore points to be found
• Disabled the Hibernate function to free up several GB's, but the computer quickly filled-up within a couple of days.
• Disabled the Backup function.
• Deleted temp files from my user profile
• I also run into problems trying to install the security updates from the Windows Update function.  I haven't been able to get the security updates to install for a couple of months now.

Anything thing I do that free's up space will only work temporarily.  The c-drive will continue to fill up in a matter of minutes or hours even if I'm away from my computer during that time.  

The strangest part is that if I right-click on the c-drive in My Computer, it will show that the 232 GB hard-drive is nearly or completely full (0 bytes).   If I open the c-drive, select all the files and folders in it and right-click, it only shows about 51 GB's of storage space used.  This does affect my computer greatly when trying to save or print even small files that only take up a few KB's.  Is there any other fix that I haven't tried yet?

I ran the WinDirStat utility but that doesn't show me anything other than the 51 GB's taking up storage space.  Also, my hard-drive is not partitioned.