Hard drives are huge these days (I have a couple drives in my computer with a total of over 1 TB of space), but that doesn’t mean that it is infinite. More important, having lots of stuff on your hard drive can slow down your computer and make some tasks, like defragmenting, take much more time. Sure, you can see how much space you have used and how much is left in Windows by looking at the drive properties, but wouldn’t it be nicer to see exactly where things are? In an easy-to-interpret, graphical format: Then here’s the utility for you: TreeSize Free.
It’s so simple to use it’s pretty hard to even have to explain it: you have it scan the drive in question and it will show you how much space is being used by every folder on your drive. If you’ve got gigs of old installer files lying around, or backups you don’t need anymore, this will help you see what’s taking up the most space. It won’t tell you what’s safe to delete and what you need to keep: you need to do your own research on that. But it will tell you where to look, and that’s most of the battle.