First get a very bright flashlight and shine it into the screen, if you can see parts of the screen like loading screens, text in the top left side of the screen or a windows loading screen then its most likely the inverter board for your screen. In laptop LCD screens there is usually a single screen length Mercury-Containing Light Bulb that is powered by a PCB board that takes a low voltage and brings it up to a much higher for the bulb to use. (This bulb is in the screen near the bottom, assuming your screen is LCD and not LED lit) ** You may even have forgot to reconnect the Inverter Board back up to the new LCD as well **
If there is NO screen activity you might want to consider that when you put the laptop back together you forgot to re connect the screen to the motherboard. As mentioned above check the cables and "re-seat" or re connect them to make sure they are in there good.
If you are sure this is not the case then check to see if the hard drive LED activity light is flickering. You may even know at this point whether the computer fully boots up by being able to hear a operating system logon sound or something of that nature.
If you end up thinking you need more parts or a new inverter board contact me, i believe we have a few dv2000, 5000, 6000, and 9000 laptops i can find parts for.
Or there are some inverter boards around the internet: