Setting it upFirst, make sure you're running Windows 2000 or XP. Sorry, it doesn't work in Vista or 7.
Download the installer (regular 32-bit) (XP x64).
Run the downloaded file to start the install wizard. It has boring template text, so just keep clicking Next.
Now the Folder Size column is available to Explorer, but Explorer isn't displaying it yet. Open an Explorer window in Details view.
Right click on the column headers to see a list of columns you can add. Choose Folder Size.
Now we can replace the existing Size column with the new Folder Size column. Right click on the column headers and uncheck the Size column. Drag the Folder Size...