Delete your account from Orkut

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Orkut

By doing following steps you will deactivate Google services associated with that account, such as your orkut profile, your iGoogle page, web history, Joga profile and Gmail account. Gmail username will not be reusable. That means nobody (and you also) can register it.

Navigate to the Google account delete page. If you are not signed on, you will be prompted for your email/password. If you don't remember your login info, you can reset password.
Choose services you would like to delete by checkboxes
Enter your password for confirmation and click 'Delete google account' button

Here's screenshot of the account delete page: