I think battery related problem
 

Ok, so today, i went and had my old battery tested because my car was starting to get really really hard to start and the battery would die from my rolling up the windows, SO after i changed my battery with one that the nice people from O'Reilly gave me a new battery, soo the first time i started it, perfect. but when i put it in reverse stalled. started it. drove off fine. then the next time at my house, stalled when i put it in drive. so i let it idle in drive then reverse for like 15 seconds, and my idle was around 400rpm and my car barly stays running is this a battery problem or something else. It never did this with my old battery?

Sounds like an alternator to me.. Sometimes, they will give intermittant charges when they are getting ready to die.

Check your cables for corrosion, not just the terminals, but the cables themselves.