petjelly, Go buy a can of compressed air. If you find two for the price of one get both. Trust me when I say that the can of compressed air will work. If you remove the 4 screws you were talking about your entire power supply will come out. if you are not technically inclined to pull it out and put the correct power supplies back then I wouldn't mess with it. Make sure you clean your processor fan with compressed air also. All that dust can and will cause problems. I clean mine once every two or three months. By cleaning it that often I hardly have any build up at all. To top it off, you should probably buy two cans of compressed air anyway. You don't want to go through one and still have dust bunnies!