battery drains overnight on my 1996 range rover.

positive is touching ground somewhere and i can't find it, it seems to be more than one place. i was told by mechanic it was the computer under passenger seat so after searching found one in europe for $500 and still has problem. I am now disconnecting everything one by one but there is a lot of electrical things in this truck, also when i start the rover the warning display says windows are open when there not and sunroof is open and bonnet is open and windows most times don't work along with sunroof and door locks ect.