Car won't start

I changed the battery on my Toyota Corolla
yesterday because they tested that it was reading
low. I went to work the next morning and came
back home and starting my car both those times
did sound a bit funny like I was a little worried it
wouldn't start but I made it home. I just tried to go
somewhere and start the car and it is completely
dead. I had my brother in law look at it because he
works for Toyota and he is thinking that it's the "kill
switch" from the alarm or something to do with the
engine. It won't even make any noise at all when I
try and turn on the car but all the lights and
windows,etc work so I know the battery is okay. I
just want to know what area I should be looking into
maybe and want to know if I should be worried
about replacing something or actually getting a new
car? Help!