You are not the first to note that. Uninstall both browsers and just put in the one you intend to use.
What happens?
Bob
HELP! I am running xp with sevice pack 2,I have been using Firefox0.92 for some time and found it to work really well.When Thunderbird 0.71 came out I downloaded +installed,all seemed ok.Now none of the hyperlinks will work,I cannot access help,release notes,or the Thunderbird site from the start page,in short I can send/receive mail but do little else. Is this me ? I am not an expert ,just a newbie homeuser.

Chowhound
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