Phone won't turn on - Samsung Galaxy S II My Galaxy S2 won't turn on. It just keeps flashing the Samsung Galaxy S2 screen.

I turned it off, then held the power button and the down volume button and a screen popped up with the green android. It says "downloading do not turn off target". How long does this take to download?
Check out this solution: http://www.widefide.com/mobile/samsung-galaxy-sii-not-booting-heres-the-solution

It was written by me years ago and helped a few who had their S2 bricked.
Follow in order: First soft reset, then hard reset and if it doesn't reboot even afterwards, move on to the third (advanced) step.