Image via WikipediaOver the years I have used many different programs to look at hard drives in order to see what is taking up all the room. Some applications are great in that they display the information graphically. But the absolute best app I've used for this purpose is also FREE. WinDirStat (for win xp/vista/7) is available in an installer and as a portable application (I love portable applications).
One of the best things about WinDirStat is that not only does it display the make up of your hard drive in graphical and tree format, as well as providing you the option to display free space, it also color codes it and let's you click on anything and delete the file(s)/folder(s) by pressing the delete key.
Recently my 1TB backup drive gave me an error that it was full. I ran WinDirStat on it and found at least 10 occurrences of the same outdated 1gb file. I also found there was some old recycler files from a previous computer, another 9gb freed. By the time I was finished I had freed up over 600gb! Not bad for 30 minutes work.
What's even more amazing is you can run this app over a network. So I periodically use it to clean up my network shares. Because it's portable there is no installation and I can run it on virtually any windows box I come to.
I highly recommend this software to everyone who uses a windows computer.