How to get a totally clean FF install?

[gkuljian]

I had a really old version on a computer that I'm now using. I have updated, using the latest version, but it won't completely update. It keeps all of the old plugins which I think are causing me trouble. Plus it doesn't play some video (youtube), which I think is related to a not totally fresh installation. Is there a way to get a totally fresh install? Do I have to uninstall and then clean out the registry for it to not remember the garbage that's preexisting?

I forgot to mention, one of the reasons I'm posting is because when I go to install some addons they say I can't do it because I don't have the latest version. Weird.

[James]

Plugins are not actually installed in Firefox like Extensions but are on system. You may be able to uninstall them in add/remove. To see where they are located on system type about:plugins in Location (address) bar.

Youtube uses the HTML5 player for new videos and since Microsoft does not support the EOL WinXP with codecs and media feature packs like they do with Vista and newer. https://www.youtube.com/html5/

Many Extension authors are supporting Firefox 57.0 and newer and are not updating their old legacy versions. You may need to scroll down the Extension page for Version Information and See complete version history to see all of the versions. You may need to scroll down a bit for a version that says it works with Firefox 52.0 in range.

[Brummelchen]

Plus it doesn't play some video (youtube), which I think is related to a not totally fresh installation.

its all caused by profile.
but it wont help you a lot because you still use XP. latest firefox for you is still v52esr but nothing can raise functionality of XP nor security.
plugins are part of concerning software, not firefox. uninstall plugins with software or disable them in firefox

[gkuljian]

Aha, so it's XP that's keeping the newest version from installing. Thanks!

[James]

Firefox 52.0 and newer Releases including 59.0.1 requires Windows 7, 8, 10. The Firefox 52 ESR is the only current version that can run on WinXP/Vista with current being 52.7.2esr and 52.9.x esr out on June 26 will be the last.

[therube]

Simplest thing, IMO, would be to start with a new, clean Profile & go forth from there.