Here's a visual breakdown. Of course, my menus and texts are in French.

Right click on c: -> properties, you arrive here:
<img src="http://legardinia.free.fr/screen1.jpg">


Now click on the button called "disk cleaning" (where "nettoyage du disque" is on mine), after it scanned your hd, you'll arrive to this screen:
<img src="http://legardinia.free.fr/screen2.jpg">


First uncheck all boxes in that screen. Now click on the "other options" tab (where "autres options" is on mine), you'll arrive to this screen:
<img src="http://legardinia.free.fr/screen3.jpg">


Click on "clean" ("nettoyer") in the "system restore" ("restauration du systeme") area. When asked to confirm, click on yes, then when you're back to the third screen, click on ok, then yes.