I have a 2004 Pontiac Grand Prix that has sat for about 6 weeks;now when I go to start it witha jump it just clicks and won't turn over and start?

While I agree with Jim, a car with a strong battery in it should easily be able to sit for 6 months and start with no problem without disconnecting anything. I agree your battery is likely worn out. They only last about 5 years. If something had been left on in the car you wouldn't even be getting a clicking sound. Of course checking the battery connections to make sure they're tight before you do anything else is also a good idea.

Thank you all for the help; I took the battery out and had it charged overnight at batteries Plus; put it back in and it started right up! live and learn. Thanks again