Vostro 1500 does not charge

I opened my laptop to clean it using the manual on Dell website and when I got it back together it doesn't want to charge. When I plug it in the light on the charger goes off and a squeaky sound can be heard from the charger.
My friend has Vostro 1510 and mine and his chargers work with his laptop, but not with mine. So anytime I plug his or mine chargers the light on it just goes off and then it has to be unplugged and plugged again in the socket to restart it. I believe there is some sort of protection in the charger, other than the fuse. Without the battery the laptop does not work.

Please help me with some ideas. What have I done?
My laptop is currently working just fine using the battery, but it will soon die and then?

 

this we need to enumerate

you might have forgotten a step or you might have displaced a thing or a wire or you might have grounded something

 

If the light on the charger is going out, it means the charger is being shorted. That probably indicates that you grounded something or messed the power circuitry on your motherboard for good (either with static discharge or whatnot). Probably take it apart, put it back together again, and hope for the best?