Help please

[Jamiecornfield]

I've had a squeling noise coming from the engine when I first started the car for a few days, it happens for the first few minutes of the car running, more so when the battery has been used also when I turn my steering wheel full lock. I assumed it was the serpentine belt, however when driving home yesterday my car lost all power, and was making a bit of a clunking noise, The battery light also came on and I lost all power steering. Again, this pointed to the serpentine belt snapping. However, I've looked at the belt and its there, it's even spinning when the car ignition is turned. When the ignition is turned the car won't turn over, I can hear a spinning sound but won't fire up. I've put it in first gear and turned the ignition and the car pulled forward so starter motor is fine. Completely baffled any help much appreciated