I have used all five authorizations for my itunes account but no longer have access to any of those five computers. Is there a way to de authorize all my accounts from another computer or from my ipad?

Use the Deauthorize All command documented inthis article, or if it isn't an option, the 'contact iTunes Store support' link at the bottom of it.

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If another computer has iTunes, you can sign into it under the Account menu. you'll then see an option to unauthorize all computers. It doesn't matter if you unauthorized a legitimate one. You can re-authorize the one you'd like.