Windows Vista Hard Drive Space does not add up

Hello everyone, I am running Vista and when I click on Computer, the hard drive (C tells me that i have 199Gb free of 288Gb, but I can only account for 50Gb, I have run Treesize, and it tells me that I am only using 50Gb of the C: as well. By my reckoning, I have 39Gb missing. Any thoughts from you clever folk?

 

Unhide your hidden files and folders to see everything on your C drive. May be some that you are not counting.
Also some AV and firewalls can create some massive log files.

 

Thanks, sounds like worth looking into, how would I go about that?

 

Thanks, but they are already un hidden, I would have thought that any AV or firewall files would be stored on my C drive, it is the only drive there is, so all files must be on there n'est pas?