The top button is the phone button if I remember correctly. I think in order to turn it on you have to press the little indented button on the bottom right corner. I don't have my old 7290 around me to say for sure but if I remember correctly its that button.
Yep. The power button is on the lower right corner. Tapping it will turn on and off the backlight. Holding it for 3 seconds will power the device off. The black button on top is the phone button, similar to the green phone button on the newer devices.