Changed URL locked me out – W – “Cookies” issue

Long story, as they all are. I was learning how to create children pages. I wanted the page header link to take me to the blog home page, not the web site… In Admin Options I change the URL from http://www.mypage.net to http://www.mypage.net/wordpress/index.php… OOps. Now I am totally locked out. When I try to access I get the “cookies must be enabled”… which has not been an issue ever before. I have been using 2.3.1 for weeks with no problems.
I have replaced all the files in the WordPress “root” directory, and all the files in the Admin directory. I had made a local copy of all these a week ago. But this has not allowed me in to the page yet. I have a backup of the PHP files, and can drop and restore if this is the problem, but hate to do so since something *could* go wrong. The question is = if changing the URL as I did could lock this up, which files does it write to that I should replace? I did search but never found a real fix for the cookies issue, so hopeing with this information someone can tell me what needs replaced.
Thanks,