I have noticed a lot of people on the internet having issues with their hard drives filling up "mysteriously" and they are not sure what to do to reclaim some of that disk space. I've already written a handful of articles that touch on various consumers of disk space, so I am going to bring all of them together in one place for your convenience. I will keep adding to this page as I write more articles that are along these same lines.
One file that is often the culprit for using a bunch of disk space is your hibernation file (hiberfil.sys). Instructions on how to remove it are at http://nerdsknowbest.blogspot.com/2013/01/how-to-delete-hiberfilsys-on-windows.html
Along those same lines, your page file (pagefil.sys) can suck up a lot more space than it necessarily needs to. Instructions on reconfiguring your page file to save disk space are available at http://nerdsknowbest.blogspot.com/2013/01/how-to-configure-your-page-file-to-save.html
Shadow copy storage can use a use a lot of space as well. You can set a limit to the amount of storage shadow copies use on each drive in your PC and save disk space by doing so. Step-by-step directions on how to do that are at http://nerdsknowbest.blogspot.com/2013/01/phantom-space-used-in-windows-7-windows.html
Your $TOPS file can build up and become rather large as well. You can reset this data on your next reboot and free up disk space. http://nerdsknowbest.blogspot.com/2013/01/phantom-space-used-in-windows-7-windows.html will walk you through how to do that.