I don't know what it's called, the rear windshield??? But anyway, I can fainly see out of it because of the disgusting brownish stuff that built up during the years. Is there anyway of cleaning it, so it will be transparent or do I have to replace it? Can I replace it easily???

Thanks, D-Dogg

Yeah, Meguiar's has 2 kits, 1 is 1 step, the other is 2 step. You can get them at www.z3solution.com or maybe the local Pep Boys or AutoZone have them.

Also, BMW has some stuff, comes in a tube like toothpaste, Part # 81-22-9-407-665.

But the best stuff I've used to date is from Griot's Garage, the plastic cleaner/polish, 1 step, goes on easy, and comes off easier (requires less elbow grease than the others and gets the best results, in my experience). www.griotsgarage.com

I've used Renovo (English product) with great results. It can be found here: http://www.properautocare.com/renplaswinpo.html

Edit:
I've also used the Plexus cleaner (basic cleaning) and it great too. You can find it at the same place.

D-Dogg,
I use the Meguiares 2 step....Mirror Glaze #10 polish and #17 cleaner and they have kept my window clear for over 4 years now. The only thing that it doesn't remove is that L-shaped rub in the lower corners where the edge-trip from the top corners lays on the wider lower corner surface when the top is down and ......lol with that!

As for replacing, yes it's as easy as calling the dealer for an appointment and dropping the car off! The window held in place with a zipper but I've been told that this is absolutely not a DIY project, even the dealer tech told me he doesn't like doing it.
Mike