DiskBoss is an interesting tool that comes packed with useful hard drive-related features. Although as this is the free version, it does also have a significant restriction (more on that in a moment).
If your hard drive is running short of space, for instance, then the Analyze tool will show you which folders are grabbing the most drive real estate. The program's Classify tool gives you an alternative view on how your drive space is being used, revealing which file types are using the most drive space. And a rather basic Cleanup tool will then delete your temporary files, IE cache and so on in just a click or two.
An easy-to-use Sync tool will quickly synchronise the folders you specify. The default settings worked well for us, but it has all kinds of configuration options available, if you need them. You can choose how many threads will be used to process the files, for instance, allowing you to create a balance between sync speed and the performance impact this has on the rest of your system.
There's also a simple Search tool, a duplicate file finder, and tools to create hash signatures, file system signatures, and a host of other handy features. A small example: when you're browsing your drive in the Explorer-like file viewer, if you select some files, then right-click one of them, you'll find options to copy their names or details (that is, name, size and creation date) to the clipboard. It's a tiny thing, but a useful timesaver, and something that Windows Explorer still can't manage on its own.
The restriction? DiskBoss won't process more than 500,000 files for any one task, which is likely to be a problem if you're running a PC of any size. And there are several other features that are only available in the paid versions. Still, there's enough power here that you may still find the program useful, and of course it also works well as a demo for the commercial builds (of which there are several). You can upgrade from only $25, and the full details are on the DiskBoss site.