Here is what I would do and probably in this order of importance. It does sound like the hard drive has failed or the system is corrupted on that drive to the point that the computer will not properly load and show the desktop. The driver for the hard drive might have gone bad.
First you want to try to get the schoolwork off that hard drive. I hope you have an external hard drive that has a system installed on it. If not then you will need an external hard drive to copy your files off if you can get the bad hard drive to mount. If that second hard drive does not have a system, then boot from a CD. A bad hard drive just might be seen once or twice just before never. The more times you try to boot a computer with a bad hard drive and not be prepared to copy the data off is foolish, in my opinion. You must have the back up dive connected and TURNED ON before you boot the computer. Put your ear to the laptop when you boot the computer and see if you can hear the hard drive spin up and you might even hear the swishing noise of the head passing over the platter during the boot process. If you hear the spin up, good. If you hear the swish of the head, even better. You will do this listening only after you hook up an external hard drive. Pray to the computer gods that the laptop hard drive spins up and shows. If it does show, then copy all the files to the external hard drive right away. You might never get another chance.
Step two is when the hard drive just will not mount and be seen as a viable icon on the desktop. If you have Drive Genius software you just might try to run it, but it is my guess that it will not work. You will then need a program like Data Rescue II, data recovery software. I have never used it so I cannot add any comments toward its use.
If you end up needing to buy a new hard drive for your computer here is a neat trick. Technical Support at Glyph told me that they partition their hard drives into no less than two partitions. They found that it was much easier to resurrect a hard drive failure if they had two partitions to work with. As a practice, I always make one partition very small and stuff a lot of my utilities in that partition that I would need in case the hard drive would fail.
I hope this helps. Good luck.
