Remember the good old days when you were convinced you'd never need more than a two gigabyte hard drive? But now your 160-gig drive is slowing down, filling up with video, music, photos, and web clippings. That "Low Disk Space" message may come a lot sooner than you ever expected. Where did all those gigabytes go? To free up space on your hard drive, your best bet is to start wiping out huge files, but there's bound to be hundreds of smaller files that aren't familiar, because they were likely loaded when you installed your applications. Don't waste time guessing what 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, giving you a birds-eye view of what's taking up most of your space.

The free, open-source utility WinDirStat can display your disk usage with a color-coded map that shows what file types and folders take up the most space on your hard drive. Using WinDirStat, it's easy to identify the biggest space hogs. It provides a 3-paned view: tree view, list view, and treemap view. The treemap represents each file as a colored rectangle, the area of which is proportional to the file's size. The rectangles are arranged so that directories make up rectangles that contain all their files and subdirectories. If you select a folder in the folder tree, the area on the treemap is highlighted for easy visual reference of what's taking up how much of the space. Similarly, if you select a file type from the list view, the areas on disk taken up by that type file (let's say, MP3s or AVIs) are highlighted within the tree map. Select files by folder name, file type, or colored rectangle, and delete or move them from within WinDirStat.

Like WinDirStat, multi-platform (Mac/Windows/Linux) 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 (if you don't already have it on your computer) in order to run it. Word is, this is a utility best used on Macs, as it may falsely report trojan viruses on Windows systems.

Many thanks to Lifehacker.com for this valuable tip!