My Users folder is over 17GB but has almost nothing in it
Solution 1:
Go to Tools -> Folder Options -> then View tab.
Make sure your settings match this picture:
Solution 2:
While Chris Tarazi seems to have answered the question above, note that you can use the free application WinDirStat (Windows Directory Statistics) to get a very detailed view of your SSD or HDD layout. It shows all your files in a hierarchical graphical view. If you're wondering what the biggest files are in your file system, it will easily show you.