A separate window popped up with a message saying "There is a new Codec Pack version. Install new version now for better performance." Is this legit?
If I say "ok" will this cause a security problem? What codec pack version is this referring to?
Alle svar (2)
Very suspicious, I definitely would NOT install it.
The StartNow extension is something that most users will want to remove. Check out this earlier thread on that topic: How do I get rid of startnow toolbar and webpage?
Note that you still seem to using the old google.com/firefox site as home page.
Google stopped supporting this page quite some time ago and has hard coded a message that tell that you use an old Firefox version.
You can use the SearchReset extension to reset some preferences to the default values.
Note that the SearchReset extension only runs once and then uninstalls automatically, so it won't show on the "Firefox > Add-ons" page (about:addons).