Noone Knows whats wrong with my car help!!?

[Melanie]

I have a 95 sunfire pontiac. The other night I was leaving and as soon as I turned on my air everything went dark no headlights or anything and the brake was hard to press so I slammed it into park cuz it seemed like the brake wouldnt work. Now all of a sudden the daytime running lights (which I never knew I had) goes on & other hazard lights on my dashboard go on when I move my car into drive/reverse its like as soon as i move my shift everything goes on & when im driving my radio will go on & off and right be4 it does that theres a sound like wen ur driving in snow and u press the brake and it trys 2 stop but makes that noise I had my radio installed for a couple yrs now so what could be the problem???