1999 Passat battery/computer problem

Hello everyone!
I've just got a 1999 Passat and I already have a problem:I replaced the battery and now the car is acting weird:almost all the lights are on(CHECK ENGINE,BRAKES,AIRBAG...)the car is stalling and I can't get it to run.Actually,sometimes is running and then it dies suddenly.Also,the air conditioning is working on and off and the cassette player is completely dead.Any advices?I suspect is the computer but I don't want to go to the dealer without my homework done.I want also to mention that the engine is turbo 20 V and the transmition is automatic.
Thanks

Hello everyone!
I've just got a 1999 Passat and I already have a problem:I replaced the battery and now the car is acting weird:almost all the lights are on(CHECK ENGINE,BRAKES,AIRBAG...)the car is stalling and I can't get it to run.Actually,sometimes is running and then it dies suddenly.Also,the air conditioning is working on and off and the cassette player is completely dead.Any advices?I suspect is the computer but I don't want to go to the dealer without my homework done.I want also to mention that the engine is turbo 20 V and the transmition is automatic.
Thanks
I had the exact same problem, I took it to the dealer and they reset the computer fault was stated to be to low voltage now the Brake ?ABS light come on and goes off I think that might be brake pad sensor or some thing but the reset cost me 40 bucks I guess it was worth it let me know what you decide maybe your will react differently than mine.