cant get past mojang screen

hi

ive not been able to log on to my Minecraft on my pc for months now it gets to the Mojang screen, loads up almost to the end then does nothing else I need to manually turn my computer off to get off the screen. Ive tried uninstalling it and re installing the game but this hasn't worked ive also read up online and it seems its happened to a lot of people what do I do as ive tried everything online that's been suggested 

many thanks

colin