(Note: screenshot above here may or may not show up instantly.)
As mentioned in an other recent post, I've been using a nifty little visual drive map freeware -- WinDirStat -- for many years.
It hasn't been updated since 2005, it's 32-bit but works just fine on my Win7 64-bit.
One can customize it, including what color to use for map highlighting as mentioned in the screenshot here of my current state of 128 Gb Samsung 850 Pro SSD as well as the highlight and "pillow height" of the quilt squares. The product page shows multiple drives all at once with the default shiny-pillowy look which I toned down.
One can choose one drive or partition or multiple ones at a time. It takes a minute or so for multiple drives to be scanned for the maps to show up. The larger the drive content, the longer it takes but its all pretty fast relatively speaking. As long as the little "Pacman" is rolling back and forth in the bottom status bar, it's still scanning.
It's really helped look for the biggest "quilt" squares representing the largest files/folders and then deciding it I really, really need those on my OS. I've reduced my original OS from +/- 85 Gb to the now 52.3 Gb. Spring cleaning in winter... :)
I could and may at some point nuke the largest green colored files in far upper right side (Cubase HALion VST sounds), but those are tricky to move to another drive without re-installing Cubase. For another day.