My friend's 2000 Seville has a dead battery. That explains the first part of why it won't start. The car was sitting for a few weeks. When he tried starting the car...not surprisingly...nothing happened. I tried jumping it from my car. The lights, alarm, etc. all came on as soon as the cables were attached. However, when he tried to start it, the engine made a high-pitched kind of grating noise until he turned the key back. We let it sit with the cables attached for a bit longer, then tried again. Same thing happened again.

It seems that the battery will likely need to be replaced, but why does the car not start when the cables are attached?

Starter? Battery? Both? Something else?

Any help or tips you can offer will help. Thanks very much!