Minecraft wont start

I was playing minecraft and went off to leave, once I got back minecraft wouldn't start, now every time I try to launch minecraft it immediately crashes. I have looked this up and apparently this was a thing but I have tried basically everything i have taken out all mods but it still doesn't work. My brothers minecraft however works fine on their computers, this means it is a problem with my computer, I use windows and have gone to %appdata% looked through everything but didn't find anything wrong, please if there is any way you can help tell me.