why wont my car start up?

If you turn the key to crank the engine and nothing happens, most likely the starter motor has gone or perhaps a bad earth to it or a loose connection on one of the wires.

it sounds like a starter problem.

the squeal is another problem due to your drive accesory belt

The squealing is most likely to be either a worn belt that needs to be replaced or a loose belt. As for the not starting I would start with simple things. If there was nothing when you did try to start the car start with getting the battery tested. A auto mechanic can sort the squealing belt and test your battery to make sure your car battery is still healthy.

If the battery comes back fine I would start to think about the fact it could be the starter motor about to die.

If the car still will not start other things it could be a computer problem, ignition like has been mentioned. If it is a car with a computer on borad then it could be a problem with the car not recognising the key as the key sends a code to the car allowing the immobiliser to disable and the car to start. If the computer is not getting that code from the key then this could also be the problem.

There is a lot of things it could be. However, if there is nothing when you go to start the car start with battery.

your question is like asking on here "may arm hurts, what's wrong w/it" !! you need to have a mechanic inspect the vehicle

starter or ignition switch