How to fix stereo? 2000 ford fiesta flight

Okay so basically I removed the stock stereo to put in a aftermarket one. However when I installed it there was no power. So I tried putting the old back in but still no power. Doesn't turn on at all. I checked the fuses and the wiring and nothing seems to be out if the ordinary. Can anyone help with this? What else could have gone wrong?

Asked May 15, 2014
Edited May 15, 2014

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