Help! My car keeps dying!

About two weeks ago, my car battery died. After I jumped it, it ran fine until today. After I jumped it today, it ran for about 15 min and then died again. When I jumped it again, it started, but as soon as I put it in drive, it died again. Is this the battery, alternator, something else? Please help. :banghead:

P.S. my car is a 97 Cutlass Supreme with the 3.1 engine

I'd say it's the alternator, if the battery connections are clean and tight.

and Welcome to AF!