hi my 2002 galant ES starts up just fine but then cuts off immediatlely afterwards and then if i try to start it again it just makes the noise like it is going to start but it doesnt....there is also this green light that comes in the dash, it has a car and a a key diagram inside it and its to the far right of the dash...what could this be...hopefully not the alternator cause i just replaced it 6 months ago

Yu are having an Immobilizer issue. The immobilizer unit is not properly reading the key. The immobilizer unit is sending an error and the ecm is sutting off the fuel injectors etc.

ok thanks lol i actually realized that i was using an old key. i told the dealership i lost it cause i thought i had and they gave me a new one and programmed it to my car. so when i used the new key everything worked fine. but i am having another issue. When i turn my A/C on it makes this nasty clicking noise from the engine...any ideas of what this could be.

Hmmm , no . I had one do this a long time ago but the A/C compressor bolts had needed thightening , thats the onlee experience i had wit a clicking noise when the A/C was turned on. I suspected the A/C compressor had been changed , so i checked and the bolts werent tight enough . Perhaps the heat sheild if anything else.