If you’re having troubles accessing your blog via the Blogger sign in page just because you’ve forgotten your Blogger password or because you’ve forgotten the Email account you used for registration, Blogger offers an account recovery tool which you can use to resolve the issue on your own.

If you don't remember which email address you used to log on to Blogger, go to www.blogger.com/forgot.g and enter the URL of the blog you're trying to gain access to. You'll be given a hint about which email address is associated with that blog, and you will receive an email with login instructions at that address.

If the recovery tool does not resolve your problem, go to Google Accounts Help Center which has more detailed information about recovery.

If that does not work and you don't have access to your old email and cannot remember your password, then you are out of luck. The only other way would be to obtain a court order asking Google to hand the Blog back to you assuming you can prove that the Blog is yours.

[FAQ] How Do I Recover Access To My Blogger Account, Without Use Of The Backup Email Account??