when i try to install firefox again it says the computer must be restarted to finish uninstalling previous version, but when rebooted and tried again it says the same thing, What do I do?

Please try this: Copy the files formhistory.sqlite (or formhistory) and places.sqlite (or places) if they exist and delete the entire Mozilla folder in %APPDATA% and also the Firefox folder in Program Files. [https://support.mozilla.com/en-US/kb/Backing%20up%20your%20information Please see this.]