no display recognized, external dispay works
I'm not a rookie at things, but I bought this 17" macbook pro 1,2 on ebay. it had only a 120GB hard drive, so i tried to upgrade. This did not go as planned (whole other issue), so i put the original HD in and started it up, got the sound, keyboard lit up, but no display. Connected to external monitor, and everything works fine.
Did you check the LVDS connection? Try unplugging it and plugging it back in. There should be no reason that the display would go out when are replacing the hard drive, unless you damaged something on the board on accident. Make sure you are always grounded during repair and always make sure to disconnect the battery!