Hi, Sounds like you gave up with it? No way replacing the battery should do this....unless something seriously shorted out on the board, bad static discharge zapped it, or you have a bent pin on something. I would check the power cord, maybe try another....check the monitor cable for a a bent pin, too.
If nothing at all happens, no sounds, no fans spin, no lights>
1. Does the power supply have an ON/OFF switch on it- on the back of the computer, where power cord plugs in....a rocker switch?
2. Outlet where you are plugging it in the wall works?
3. Naturally, try a new battery.
4. Just leave the pc plugged in overnight, but off...power flows to battery when machine is off, and plugged in. Maybe just too low a charge. (Normally, they start, but put up a message about low battery state, probably not your problem)
5. Motherboard connectors from power supply might be loose...big white plug, two piece or one....if its a two part connector, side by side, that plugs into the motherboard...the two black wires have to be next to each other when you plug them down into the connector. Can kill a board if you reverse these connectors. The one piece, or ATX plugs can only go one way.
6. Power switch- the one from the front, or power button, has a thin set of wires to the motherboard, check it's connector. Did you move any of these little wires, LED lights, Reset button, etc??
Reseat the video card if lights, fans work and you just get a blank monitor screen. Also reseat the memory modules.
7, Some boards are pretty easy to crack if you push too hard down on something, so take it easy pressing anything on them...
8. Try a different power supply----if the computer is a DELL, you must use a DELL power supply!
I won't be replying again, unless you ask for further help, others might, if you want to close the thread, just post that you do.... Thanks!