A great tool for visualizing what is taking up all of your disk space is WinDirStat. It displays all of your hard drive’s files in a visual form allowing you to easily see what is using the majority of space and seeing what to delete. WinDirStat also lets you view what filetypes are taking up what, so you can see if your avi collection is taking up most of your space or any type of files you use.
You can download WinDirStat on their offical site here.
