Identify how much disk space you're using with WinDirStat. Based on the Linux application KDirStat, this great piece of freeware offers you an informative visual display of your hard-drive usage. It can also analyze your local devices. Depending on the size of your disk, the initial WinDirStat scan may take quite a while, so be prepared to go grab a cup of coffee for 5 to 10 minutes.
When you return, you'll see all of your files (for the drive or directory you decided to scan) displayed in a rainbow of colors. WinDirStat assigns colors to each file type, such as MP3, ZIP, EXE, JPG, and so on. By default, the files that take up the most space are colored blue, the second heftiest are red, and the third largest green. After the first 10 color-labeled file types, the rest appear in gray--but you can change these settings and colors through the Options menu.
Once you've identified where your disk space has gone, you can then more easily decide where you can save space. WinDirStat is loaded with features for managing your files, such as the ability to automatically delete files without even bothering with the Recycle Bin. It's one of those tools that you didn't know you needed until you started using it, but once installed, it's hard to imagine life without it.