Remember when you were sure your computer had all the hard drive space you'd ever need? Gigabytes sell for less than a buck a pop nowadays, but with video, music, photos and web clippings hogging up hard drives more and more each day, that "Low Disk Space" message may come a lot sooner than you ever expected. Where did all those gigabytes go?

If you need to free up space on your hard drive fast, your best bet is to start wiping out the big space-eaters right away. But don't waste time guessing who they are; there are easy ways to inventory what's clogging your hard drive. Free tools for Windows, Mac and Linux map your hard drive usage so you can get a birds-eye view of what's taking up most of your coveted hard drive space.

Here are some of the tools I have used.

FosiX A lot of features and appealing visuals but 30 days trials(Download)

JDiskReport (Download)

multi-platform freeware JDiskReport also provides graphical disk usage statistics using more common pie/line/bar charts.Since JDiskReport is Java-based (hence the J), you'll have to download and install Java in order to run it.

WinDirStat (Download)

The free, open-source utility WinDirStat displays your disk usage in a color-coded map that shows what file types and folders take up the most space on your hard drive.