Unles you have a physical failure of the disk drive, we should be able to get the data off the drive. This is no guarentee, but very likely. We should be able to get all your pictures, music, and documents. If the machine needs to be reloaded, you will need to have all the CD's that came with your machine. The Gateway's usually have a restore CD case that includes all the software that was loaded from the factory. Our Aunt had a Gateway with the same problem and we just reloaded the machine. All was fine after that. I sent you a message with my contact information if you would like me to help out. And of course, there is no charge.
Since the screw was on the carpet, I dont think it has anything to do with your failure. If the screw was inside the case and rolling around, I would then suspect it may have shorted something on the motherboard. Save the screw.