Help, car is DEAD.

need some seriosu help with this.
There i was last saturday with my white j reg, all done, put new battery onit and it started up, GREAT! took it for a drive to a friends, turned it off, went to start it and it turned over really slowly, so we bumped it got about half mile down the road and POP from teh engine bay and everything on the car is now dead, smoke coming from where the battery is (at the back) took the cover off and the cables are too hot to touch (16mm2)

So i do some research and seems ive used too small cable and its cooked, today i fitted some MASSIVE amp cable i took from a breaker, got the 172 down put jump leads onit and direct to the car (no battery as its cooked) and it just sparks loads, no power nothing. i assume something is earthing out, cant find anything though, wheres the first place to look?

This car is PISSING me off.

check all the main earths ,engine to chassis , g/b to chassis leg

you not snagged the cable from front to back?

cable has been changed, all earths ok.

Had asimilar problem a few years back in my case the starter motor had stayed engaged because of a faulty key barrel, or could be motor - causes it to become a dynamo, melted my cables and the starter solenoid.

the solanoids normally pack up in the starter if the earths crap my clio done that and kept my fuel pump permantally on i brought a earth kit off ebay dun the trick