Had my '04 for about a month now. Have noticed while driving at night this annoying little green reflection spoiling my view in my windshield. Just thought it was my blue dash lights bouncing off a joint seam or something in the top plastic of the dash, but yesterday when I examined it closer, I see a slot with what looks like a bounce mirror inside of it. Do Priuses have a Heads Up Display? I'm told mine has Package 5 (no idea what that means, and there has never been anything showing on my windscreen.) And, If I have it, how do I activate it?
Just turn down the brightness on your odometer, that'll get rid of the green reflection at night. There's a brightness adjustment wheel to the left of the steering wheel, move it up or down to adjust.
The combination meter (speedo and odo) is actually inside the dash facing up and the mirror reflects it so the driver can see it. The nighttime reflection off the windshield is an unfortunate minor design error. Turn down the dimmer wheel and all will be well.
If you don't understand what the mirror is for, try putting something over it and report what you (don't) see.