Battery light on

[eamon]

I have checked the earth at the pedal it's good, as is the main from the battery. How do I locate the gearbox earth? I am inclined to think it couldn't be an earth as the windows work with no key but the radio and wipers won't. It's very strange.
How do i check if it is alternator feedback?
I have disconnected the battery for now as I need the car for a couple days and don't want it dying overnight :S
Also the battery light goes completely off when the engine is running