Don't forget the power of "Find Files or Folders" utility ("Start Menu | Find | Files or Folders..."). For example, you can use this utility to find out the largest files on your system or search for files that are possibly too old to be on your system.
Select "Start | Find | Files or Folders..."
Change "Look in" to "Local hard drives..."
Select "Advanced" tab
Change "Size is" to "At least"
Set "KB" to 4096 (for example)
Click on "Find Now"