Sounds like you are good for a new HD. Clicking or scratching noises are bad.
It means either the heads in the HD have been damaged or moved from their normal position or that you have a scratch on the platter. The HD is not able to find the data anymore because it is looking at the wrong position or because the head is jumping over the scratch.
As the HD was switched on and writing while this happened, you can be sure there is a nice scratch in your platter and your data will be hard to recover.
Try if possible to put the bare HD in the PC (directly connected to IDE or SATA). If the bios does not recognize the HD, you are good to throw it away.
If it is recognized, you could try Easy Recovery Pro or similar data recovery software to get as much out of the HD as possible before it dies (it won't work for long anymore if you have a scratch).
If you have very very very important data on your HD, you can try a professional company. But be aware, it will definitely cost you more than 400 bucks (I would say starting at 800-1000).
Tomshardware have some nice articles on that. Have a look around.