How do you open the trunk of a 2000 Jaguar XK8 with dead battery?

There are two ways. The first one is the easiest, so try this: Just below the right taillight you'll see a little chrome "XK8" emblem. In between the X and the K you'll see a little hole. Stick the key in there and turn it. The trunk should open. If that doesn't work, get some jumper cables, open the hood, and look for the fuse box on the left side of the engine bay. Take the cover off of the fuse box, and at one corner of the fuse box you'll see a big bolt with a fat wire connected to it. That's the positive wire for the fuse box. Clamp the red clamp on the jumper cables to that bolt, and clamp the black clamp to any exposed bolt in the engine bay. Hook the jumper cables to the other car, but DON'T TRY TO START THE ENGINE LIKE THAT. The Jag will have electrical power, so you should be able to pop the trunk with the fob or with the button on the dash. Once you've popped the trunk, move the jumper cables back to the battery to start the car.