when you plug in the LCD make sure you tell it to use the external monitor. this is usually done by holding down the FN key and pressing something like F5. look for the key that has a symbol that should look something like the laptop screen and another screen near it... that tells the laptop to use the external monitor port instead of the LCD screen... they usually act as a toggle between 3 modes; LCD, External monitor, and both.

also, if it is powering on at all then the lack of a battery is not the issue. LCD screens can be replaced if that one is bad, but it would likely be at least $150 for the parts and a couple hours for labor unless you know how to do it yourself.

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