Firefox Not Opening

I'm currently having problems opening Firefox on my computer on both user accounts. About last night, Firefox just got an update and my hard drive was low on space. The update failed to finish and I can't open the browser to finish or cancel it. I've cleared out a little of my hard drive and only have 845 mb for it to work but it won't. If there is another way to fix this problem please leave a comment below.

Thank you.