Brakes making noise and locking...

I got a 96 Grand Am SE. Everything was fine the day before, so I don't know what happened. I started to drive forward out of my driveway, and when I pushed the brakes, there was a grinding noise and the car just stopped really suddenly. From then on it keeps doing that. I put almost no pressure on the brake pedal, but the braking feels like I just slammed my foot down on the brakes. I tested it a few times on my driveway, then I went around the block. Stopping at higher speeds locks up the wheels so bad that the tires squeel. Also I could hear and feel some sort of grinding. It wasn't terribly loud though. The pads are getting thin, and the rotors should be replaced probably as well, but I'm not sure if that's the problem because the day before everything was fine. It just happened when I started the car in the morning. Could someone help me out and tell me what's going on? Thanks!

I would pull the wheels and look at the brakes. It sounds like the pads have fallen off the backing plates causing the brakes to lock. The other possibility is that the calipers are sticking and will need replaced or rebuilt. Finally, you could have a problem with the ABS system but you should get a light on the dash if that is what is happening. If the pads and rotors check out and you find that the calipers are not sticking take it to a mechanic and have the ABS system checked.

Is it the front or rear wheels that are locking? I agree with GTP that you have a metal to metal situation and need to change your brakes immediately, as Mr Car might meet Mr Tree in a very bad way if you don't.

I heard from someone that it could be the wheel cylinder leaking into the drum so I checked for that, but didn't find any sign of a leak. It could be a really small one. In any event, the shoes and drums are still in good shape so all I did was clean them up and sand them. I put everything back on, went for a drive, and the car brakes fine now. I'm going to see tomorrow morning if the problem occurs again. At least I know that its the rear brakes that were giving me trouble. I knew it couldn't be something as simple as worn down rotors or pads or anything like that because the whole problem occured too suddenly. Usually there'd be a period of time where it would get worse and worse. Thanks for the help guys, and I"ll keep you posted on how all this turns out.