I have a 42" panasonic TV, yesterday the screen went blank. When I plug the TV in I here a whining sound, then when I turn it on it clicks then the power light flashes seven times

Apparently the 7 flashes is not really a diagonostic code. It means that the TV is detecting something wrong with your power, and that it is shutting down for safety reasons.

Try plugging the TV into another outlet. Also ensure that the grounding is good, using a tool purchased at a hardware store.

If you are using a power bar, remove it and plug it directly to the ac outlet.

You can also unplug the TV for about 2 hours, and then try again.

Take a look here for a solution. Looks like you may need to take it in for a new chip.

Your TV may have a serious problem, Think if power is good as mentioned above, Then Repair or replace may be in order. What model, Plasma?
Do go to the link provided by HVAC888.