"Norton but from memory it has a facility to lock the homepage...

"Norton but from memory it has a facility to lock the homepage so it can't be changed by malicious 3rd parties. You might want to make sure it isn't 'checked'."

yes, and if that is the case, uncheck that function in Norton, change your desired home page, then go back to Norton and check that function again.

If the problem is not due to that, then more than likely you will need to identify that "trouble maker" hiding in your computer's registry and do a manual delection, but, and this is a big but, you need to know what you are doing. Playing with files in registry and make a mistake and you will be in big trouble.