Help, My Car Wont Stay Started!?

so i was driving down the road and my little battery like came on.. i thought ok great battery going bad i'll get a new one. Well then my abs light came on and would turn off and on.. After a couple mins, everytime i pressed the brakes the radio would shut off. I stopped at a house and then it just died!! all the lights in the car still on windows still went up (alittle slower). i got someone to jump it, and started right up i went to drive it and it died as soon as it started moving. I have a sweeky belt if that has anything to do with it or anything.. but its a 99 mazda and kinda want to know if this sounds like the alternator or just the battery or if it could be the belt tensioner or something… please help! i dont want to take the alternator off and bring it in because for 1 its at someones house tht i dont know and 2 its all the was on the bottom and hard to get at…

Suggestion:

If the squeaky belt is the alternator belt, that may be a place to start, but it sounds like the alternator. This is not an impossible fix. You can even rebuild the alternator you have rather than buy a new one since they do cost a bit of money.