Not without the admin passwords. Don't know if they are still around, but third parties used to offer a "pasword cracker" utility. If you can find such a widget, use a copy of your files and this utility to open the files. You can then open FileMaker 5's version of manage security and read the actual passwords used. Then you can use fileMaker 11 to open your original copies and use the admin password to open them. FileMaker will generate converted copies of your database for use with FileMaker 11. These converted copies may run perfectly, but chances are that some small changes will need to be made before they run perfectly in version 11.
See this knowledgebase article for more on file conversion: http://help.filemaker.com/app/answers/detail/a_id/750/kw/converting