Electrical system suddenly completely dead.

My car isn't registered yet, but I drove my 2005 around the block a couple of times last week, and it ran fine. Parked it in my driveway for a couple of days, and today the electrical system is completely dead, so dead it's like there's no battery in it, zero indication of power anywhere.

I tried both my keys and remotes, nothing. I charged the battery, but it charged up quickly, indicating that it was fine in the first place. I checked the fuse on the positive battery cable, it was fine.

I took the cover off the underhood fuse box, and looked at the diagram on the underside of it. It looks like there should be a 120A main fuse in there, but in the actual location there are just a couple of terminals with wires attached to them, and I don't want to mess with that without knowing what I'm doing.

I could try jumping it, but I think the battery is fine and the car isn't positioned well for a jump with normal length cables.

Any ideas? I just bought this car so I'm not familiar with working on them or their issues. I have no idea why the car was fine one day, and totally dead a couple of days later, with a seemingly good battery.

Electrical system suddenly completely dead.