Windows: Scanning your hard drive for unnecessary files doesn't have to be tedious. Spyglass makes it easy, and dare I say it, fun.
If you've ever used previously-mentionedDaisyDisk on a Mac, you should have a good idea of what to expect. You select the files and directories you want to scan by dragging them onto the Spyglass window, and every subfolder and file will be presented in a radial pattern that makes it easy to tell what's taking up the most space. You can click on folders within the diagram to zoom in and get a closer look at the contents.
If you see something you don't need, you can send it straight to the Recycle Bin, or open it in Explorer for a more detailed look. Some might call the graphics and animation superfluous, but I think in this case, they actually really help you diagnose a bloated hard drive.
Spyglass will also detect duplicate file names on your system, and present them in their own interface to sort through. If you only need one copy of the file, a single click will delete the replicas. Feature-for-feature, it might not stand up to the almighty WinDirStat, but it's absolutely more intuitive and enjoyable to use.