Yeah virtual memory is where it uses some of your hard drive capacity as memory storage.
Download CCleaner (it's freeware) and that should clear a decent amount of space. As would uninstalling any old software you have installed that you don't use any more.
Yeah, your hard drive is probably quite close to full of porn. Clear some old stuff out and you should be good to go. CCleaner is a good place to start as mentioned above.