Try to open folders etc and system freezes

I have the strangest problem on my husbands computer. I had posted a thread here a few days back and thought that it was just a problem with firefox as whenever you click on its icon it will connect to the internet but the window doesn't appear;I can get IE window to appear. I had done a system restore and got firefox to load but whenever I would try to check his gmail account firefox would crash. Well I am back to square 1,firefox is not appearing again and whenever I try to rightclick on any folder the system freezes. I can't get to the C drive folder or any folder for that matter. I really really don't want to do a system recovery if I can help it as he has things on there he cannot lose if at all possible. So all in all it's not just the browser acting up and I have no clue as to what it could be. I knew not to let our daughter use his computer!!

Karen