Firefox asks to be default browser every time it loads

"You may want to look at ""Setting Firefox as the default browser does not work"".

Summary:

Windows XP. menu Start/Control Panel/Add or Remove Programs/Set Program Access and Defaults (left panel)/expand Custom (icon on the right)/""Choose a default Web browser""/Mozilla Firefox
Windows 7 and Vista. Control Panel/Programs/Set your Default Programs/ etc."

"My Windows Firefox has the following sequence to stop checking for that.

Tools

Options

General tab

Uncheck ""system Defaults"" -- always check if default browser

However, if choose not to be asked when prompted, it should save that.

It could be possible that some other tool (AV? Anti-Spyware?) is preventing the change of default browser on your system.

Or, you do not have permissions to write this change (less likely but possible)."

"see here:
User.js file locks certain preferences.

http://kb.mozillazinedotorg/Preferences_not_saved

This is what solved the problem for me"

"None of the first provided advice in Google resolved the mentioned issue on my computer, but I found the solution.

The incorrect behavior obviously caused by migration from 32bit to 64bit version.
We need just to replace the incorrect paths to the Firefox main executable image in the Windows registry:

1) Open Registry editor (regedit.exe);

2) Place focus on the root of registry database (My Computer);

3) Initiate text search (Ctrl+F). Specify ""Parameter Value"" flag only, and reset the rest flags.

4) Enter the next text to the search pattern field: ""C:\ Program Files (x86)\Mozilla Firefox\firefox.exe"" and press Search button to find first occurrence, all the next occurrences could be found by pressing consequentially F3 key.

5) Replace all incorrect occurrences with next string ""C:\ Program Files\Mozilla Firefox\firefox.exe"". This version doesn't contain ""(x86)"" string.

That is all."