NEW CLIENT UPDATE [CRASH] [WINDOWS 10]

Hello,

I recently had heard about the new client update so I checked it out. I went into my League client, did the update and launched the game. After this, it wouldnt let me go to the login screen. So I closed and re opened and an error message popped up saying : "Another instance of the launcher is running" and it would automatically close. I un installed and re installed not knowing that the problem was coming from the client update. I now have to uninstall, re install and I won't even be able to play with the new client. Please fix this or tell me a way to fix it.

Thank you.