Orange And White

[Intro2]

Hey guys, long time but i have been busy installing an in car PC system to deal with dvd, gps etc have run into a small hitch which i guess someone will know anyway Celica GT (Import) just replaced the head unit (which was kenwood) with a Pioneer no problems with wires except there is an Orange/White wire from the car which has no place on the new stereo but was connected to the old stereo, any ideas what it does/is? also everything was fine on the pc front using a Belkin power inverter to drive the PC but since changing the head unit i have really bad interference on the screen when powered up even thou its wired the same as the original!! again any ideas? seems to be picking up noise off the fan in the inverter so anything to do with this litte orange/white wire?

thanks