What you could try is taking out the battery, DVD drive and hard drive and trying if the laptop responds then.
If some light up it could be the LCD screen so in that case try connecting to an external monitor with VGA and booting then to see if it works.
Otherwise I'm afraid it looks like your motherboard has been damaged and is not operating anymore or the motherboard is not getting any power because of a broken or damaged cable/connector between the power supply and the motherboard.
You can try following the instructions HERE
on how to troubleshoot a dead laptop, but at the risk of doing more damage.
Perhaps it's an option to try to bring it to a PC repair shop?
It's hard to say for sure, but I doubt it's something simple unless its one of these two things:
1. You disconnected something related to the motherboard and connected it again at the wrong place or by damaging it (you can try checking this)
2. Something fried your power adapter or damaged it in such a way it cannot supply enough power to the motherboard anymore
The second option is unlikely, the first is possible, but if you say your sure everything is back the way it was...
I'm sorry I can't be more help, but personally I think your best bet is to bring it to a PC repair shop.
I'm not sure, but my guess is that your warranty is void since you opened it. You could check this though at the website of the manufacturer.