Is your hard drive full and you have no idea why? I use this little utility called Space Use Scanner. You can download it here: www.steffengerlach.de. It shows you a graphical chart of your hard drive. You can actually click any portion of the graph to see more details about what in that folder is using so much space. [This actually points out hiberfil.sys (Hibernation file and system info) and pagefile.sys (virtual memory stored on hard disk) as taking up a lot of space most of the time.]
The screenshot is from: http://www.steffengerlach.de/. I did not make the screenshot above. Please visit the site to download the freeware.