Try connecting an external monitor and see if you get a screen. If none available, try booting normally and watch for hard drive activity such as would happen when Windows is loading. If this never happens, your laptop never completed POST. If it does, your laptop probably booted normally but your screen is unresponsive. When you first apply power there should be some sounds from the fan and hard drive as well as LED indications that the system started. You'll know what normally happens so giving that information helps narrow down the point that something failed.
I have a mt3422 Gateway laptop and when booted it has a black screen, I have tried removing memory, hard drive, dvd drive, and cpu and rebooting with no change. I am thinking video card or mother board, doe anyone have any helpful hints for me. Thank you