Laptop Screen gone blank

Hello,

My laptop is Dell XPS 1530 with Windows Vista. When the laptop is booted, nothing comes on screen, it is just blank. When connected to an external monitor, everything comes on the monitor, but nothing on the laptop screen. Then if I put it on hibernation while working on the external monitor, then remove the monitor and switch on the laptop, the laptop screen works just fine, except that I can't adjust its brightness by any method. So I am using it by putting on hibernation repeatedly and not shutting down. I have tried the above thing twice. When I ran the diagnostics test on booting, it shows the following error:

Error Code- 0321
Msg- Error Code 2000-0321
Msg- LCD EDID- unable to access EDID EEPROM

And also the test 'Do you see colored bars on screen?' works fine (The tests were done while connected to external monitor. I talked to a Dell guy and he suggested me replacing the motherboard and LCD display. Since my laptop is not under warranty, it is gonna cost a lot of money. Please suggest something.

Thanks.