i tried installing a sony head unit in my 00 and had all the wires connected, and when i tried turning it on to see if it worked, it didn't even turn on. No power got to the head unit. Then when i pluged my factory one back in, it worked. So this must mean that it has to do with the wires and or the sony headunit and don't which. any help would be nice.

thx!

I have an 04 Xterra, and the wiring setup for the stereo is goofy. The deck uses one of the screw holes that holds the CD player in place for a ground. I would try putting the ground wire to one of the screws that hold in the CD player in place and see if it turns on.
Also my 04 has 2 ohm speakers in the doors. If your 00 has the same speakers, it will more than likely force your CD player into a circuit protection mode. All aftermarket CD players (at least the ones I have seen) are only rated for 4 ohm speakers. You may want to pull out your door speakers to make sure.

thanks for the input! it helped and now my new headunit works! thanks for the help.