My 2000 Ford focus was making a grinding noise when driving the power stering went out and I look under the hood and the belt was loose what do I do... O battery light is now on.

Sounds like the power steering pump has failed.
You could take the serpentine belt off and check the pump pulley.

I just had this problem and it turned out to be the starter fuse in the fuse box under the hood, so happy it was none of the things previously posted! just one 30 amp fuse :D

They do not stretch that much. That engine uses a serpentine belt. Something has gone bad that caused the belt to come loose. All pulleys must be inspected to diagnose the problem.

You broke your serpatine belt. Needs replacing. It's a $50ish part and easy to do if you have a diagram under the hood of how the belt fits. But if it was "rattling" for a couple of weeks take it in for crying out loud. Let the mechanic look it over to make sure your lack of vechile care didn't destroy anything under the hood.....

should be a diagram under the hood or next to the fan

If the belts are making noise when you turn the a/c on, the a/c compressor or belt may have issues.

Need to check for any loose belts first .

Check belt, idle pulleys and tensioner.

Check the front drive axles and boots. A bad cv (constant velocity) joint can cause this.

I had the same exact problem with my 2003 Focus with 108,000 on it. Making right turns and accelerating was even worse. Had many ideas from differant mechanics saying it was wheel bearing, steering rack, loose heat shields, transmission...ect. Well after having wheel bearing replaced and steering rack replaced, the grinding was still there. It was finally discovered that the noise was coming from a bad motor mount on the right side. Had the dealer replace the motor motor mount and finally!!! the problem was solved. Thank God.