Try using the full off-line installer.
http://www.mozilla.com/en-US/firefox/all.html

That is what I already tried to install Firefox Setup 27.0

any other ideas?

Check for the presence of a mozilla.cfg file in the Firefox program folder to initialize some prefs.

This also involves the presence of a .js (JScript) file, probably in "defaults\pref" folder, that specifies to process this mozilla.cfg file.

If you have .js files apart from the channel-prefs.js file, that sets app.update.channel, in the defaults\pref folder then open this file in an editor like Notepad and please post its content. Also please post the content of the mozilla.cfg file.

There shouldn't be a mozilla.fcg file present unless you've created it yourself to initialize some prefs.

If you have this mozilla.cfg file then best is to do a clean reinstall and delete the Firefox program folder before reinstalling a fresh copy of Firefox.

• http://kb.mozillazine.org/Preferences_not_saved#Other_solutions

I have completely uninstalled and reinstalled and gotten the same results. the files you are asking about are not on my system.

Are you sure that you did delete the Firefox Firefox program folder?

• (32 bit Windows) "C:\Program Files\Mozilla Firefox\"
• (64 bit Windows) "C:\Program Files (x86)\Mozilla Firefox\"

Is the only file in the defaults\pref folder the channel-prefs.js file or are there other files present in this folder?

the folder is still there. channel-prefs.js is the only file in the folder. should i uninstall the program first, then delete the folder or the other way around? or does deleting the folder uninstall the program?

Problem solved thanks for all your help!