Yikes! Doesn't sound good. If it's a 4Gig drive, it's probably old and may have reached the end of its life.
Try booting to a floppy drive and then see if you can read your hard drive. If so, I highly recommend getting another HD and installing it in your computer. Then try copying it off the bad drive to the new drive.
If you can't read your hard drive at all, take it to a computer repair shop and see if they can read it.