Perhaps she's not a goner after all..

OK, so you put the car in gear and it doesn't move.
Is it an auto or manual?
Column shift or floor shift?
Your brother in law has a '75 Valiant, what are you working/having problems on?

When you put the car in gear and it doesn't move, does it try to move? Does it make any noises?
We can probably come up with a hundred different things to check, but if you give us a little more info we might can narrow it down some.
For instance, is your emergency brake on?
When you put it in gear and the car doesn't move, how much gas are you giving it?
C