There is a loud "whining" noise in the front end of my 2000 Pontiac Gran Prix?

could be a belt and tensioner, or a pulley.

Also consider that a front wheel bearing may be failing. the noise tends to get louder and higher pitch as car speed is increased. drive the car at about 80 kph and shift the trans into neutral,if the noise is gone, then it is probably engine belt related, if still there, then it may be the bearing or an axle shaft.

otherwise raise the car into the air, trans in neutral and spin one front wheel while placing your hand on the coil spring. if the bearing is failed, you can easily feel the roughness in the spring. compare it to the other side to see if one or both, or neither are failed.

Good luck

Loud whining noise usually comes from a hydraulic pump that has air in it. My first guess is the power steering pump. Next is the transmission. You need to check the fluid levels. This problem would happen whenever the engine is running. You wouldn't have to be moving.

Otherwise it could be a bearing, or something got bent and is rubbing on something that is moving. This kind of noise would only happen when the car is moving, and would get higher pitched, the faster you go.

Who changed the tire? How did they jack up the car?

The first thing we would do is to remove the serpentine belt and spin all the accessory pulleys by hand.

If you find a bad bearing you've struck pay-dirt.

It wouldn't hurt anything if you started the COLD motor and drive the car for no more than a minute KNOWING you'll have no power-steering, water pump, air conditioner or water pump to see if you hear the noise.

Check the belt tensioner.