How do u get to all the folders on a hard drive?

My hard drive seems to be adding contents to my drive, how can i get rid of the extra content?

• I own a dell studio 15 laptop which is running windows vista basic, and the other day, i checked how much free space my hard drive had and it said somewhere around 60GB or 70GB were free (out of 176GB). Last night i checked it and it said around 18GB were free (still out of 176GB). Today I was installing the new version of iTunes and i decided to check the space and it said only 17.6GB were left, but i know that itunes doesn't take up 400MB of space and i haven't added anything or downloaded anything to my computer. About thirty seconds later, I checked the space left again, and it said only 17.4GB were left. Now, about three hours later, my computer says my hard drive only has 15.7GB left, and I don't know what is happening. I have checked all the folders in the hard drive to see their size, and they only add up to about 106GB which would leave about 70GB of free space on my computer. I need help finding where the extra space went and how to get it back without completely formatting the hard drive.

• Answer:

  try WinDirStat, it can show you where and how big files and folders are on your disk. http://windirstat.info/