As for the DVD, whyteknight is right, they take a deposit along with the rental, when you go back tomorrow you can collect the money, if not me and whyteknight will collect it for you, we only charge 10QR (just kidding)

Taxi from the Airport, I'm not sure I've never read the window always starts at 18QR, I think thats the surcharge for the Airport pick up + extra 5 QR for a ticket you get to pay it before you leave the rank!!
paid it last week.