Data and drive space not adding up...compress?

I'm looking through my C drive, deleting unneeded files, doing a disk clean up, defragging, ect. I have noticed though that the size of the folders in my disk compared to the amount of space taken up on my disk don't add up. Not by a long shot. According to the properities windows of my C Drive I have filed up about 83gigs of space... but my programs and files folder is only 511mb, my programs and files folder (86x) is only 12.gb (I have vista 64bit), and then my user folder with all my downloads is only 7.4gb. I have my windows folder with 51mb, but after that there really isn't anything else of any significant size. I checked out all the installed programs and my "add or remove" menu and couldn't find any programs much larger then 4gb. That was a game I had installed.

I noticed there was the "compress files to save space" option, but I read that can slow down your computer and I didn't want to make a large portion of my files unusable. Is this a common thing or do I have a problem?

 

There are hidden files you can't see such as system restore. How big is the drive and what do you show in use vs what you have added up to?

 

My drive is 320gb. This information concerns my because I want to get an 32gb SSD to load windows and my start up programs on to it.

Right now I have 49 processes going. I have disabled many vista services, but my GPU software, nero, counter spy, AIM, utorrent, Obejectdock, dream scene, ect. all run their own process.

 

BUMP

Its a gaming computer. I want to eventually transfer my OS on to a 32GB SSD, and I need to get it down to size. Also I just like preserving disk space...