Check your computer programs listings. You may find that a program you don't know is listed. Your problem is not from Firefox, but this other program. Find and remove that program and you should be set. If you can't tell which program is doing all this, make a list of your programs and post it here.

Extensions that do not have a "Remove" button are installed by other software and are not under control of the Firefox extension manager.

Such globally installed extensions are usually found via a registry scan or are installed in a location that Firefox scans for installed extensions.

• https://developer.mozilla.org/en/Adding_Extensions_using_the_Windows_Registry

Extensions installed this way need to be removed via the settings (options/preferences) of the program that has added this extension or you need to uninstall this program via the Control Panel.
In Firefox you an only disable such an extension.

I searched this and found a practical removal method in google group, so i attached and would be glad if it helps.

1. Uninstall any Carton programs in PC control panel and Carton extension in browser add-on.
2. Search through registry for all keys containing the word corton and delete them.
3. Delete suspicious files and exe you recently installed on system32 folder.
4. If these are too complicated for you, you can run

I am still having issues with the Carton Addon trying to install. And now, when opening Firefox Nightly, I have a new one, Greppo, that does the same thing. As noted above my browser gets redirected to Amazon.com when opening, once these things have self installed, without my permission. No Malware or virus or anything else shows up on my scans, and even after doing a reg edit, they show again. I cannot figure out where they are coming from.