problem starting car...

I have a 97 eclipse and just recently I've been having problems starting it.I had it parked outside for a over week without driving it, so when I went to start it up just the radio and lights would go on then after a few minutes all the power was drained, so I jump started the battery and everything was fine until the next week when I was out of town for a couple days and came back to the same problem. I'm going to take the battery in to see if its bad (only 1 1/2 yrs old), but was wondering if anyone has any ideas of what might be wrong? I was thinking that my soundsystem could be draining the battery or maybe its the alternator? any ideas would be appreciated

If you go to Autozone the will do a free charging system test, which will tell you if your problem is with the battery or the alternator.

does it make a clicking sound? if it does then like me you have a starter problem.you can get one at auto zone for about 100$

I have a 97 eclipse and just recently I've been having problems starting it.I had it parked outside for a over week without driving it, so when I went to start it up just the radio and lights would go on then after a few minutes all the power was drained, so I jump started the battery and everything was fine until the next week when I was out of town for a couple days and came back to the same problem. I'm going to take the battery in to see if its bad (only 1 1/2 yrs old), but was wondering if anyone has any ideas of what might be wrong? I was thinking that my soundsystem could be draining the battery or maybe its the alternator? any ideas would be appreciated

but if it is the alternator how would you know. and where is the altenator