Rear windows won't open

Thanks for your replies, Booster and Islandman. I removed the screws you both referred to, and just like magic the windows could be opened as designed.

Since there are no screens on those windows, I had decided to just forget about ever opening them even if I found a way to do it, because they'd be nothing but a convenient entry point for mosquitoes and other insects. The point about exhaust fumes is also a good one, so all things considered, I replaced the two screws and won't give it another thought.

Thanks again for being so helpful.