Ok, so I drive a 2004 Mitsubishi Lancer Es... I just changed the battery, and guess what? The wires got crossed... So I figure I probably blew a couple fuses, at least... but I've checked them all and they all look in good shape, unless there's more than two fuse boxes, which I've been unable to find. The two I've checked are under the hood, and under the dash. But the problem is that, now my stereo will not get power, the light for my high beams on the dash will not show up when activated, my light on the ceiling does not work at all, and my power windows and locks do not work unless the car is running. What could the solution be?

Did you check the fusable link to your positive cable?

Your discription sounds like the ETACS-ECU may have taken a hit.

I'd suggest that a qualified mechanic look at your car.

The Radio should not be driven through the ECU and should be a 10A fuse. (Under the dash).

If the fuse is good the Radio may be a gonner as well.

First, verify again the fuses are good.
Second check the wires, looking for burned (Crispy) wires.
Third get the ECU checked out.

Good Luck.