Do you now?
"The curators are currently planning to return your Extra Balance account contributions directly back to your original address."
if you bought The DAO Tokens in the phase of creation and have paid more than 1Eth: 100 The DAO
To be precise if you bought between:
Sun, 15 May 2016 09:00:16 GMT ends Sat, 28 May 2016 08:59:47 GMT
Anyone who bought DAOs in the last two weeks of The DAO crowdfunding phase paid more than 1 ether (ETH) per 100 The DAO tokens (DAO). The ETH amount in excess of 1 ETH per 100 DAOs was stored in The DAO's extraBalance account. The balance of the extraBalance account has now been transferred into the curator's multisig wallet.
Summary
At the hard-fork block #1,920,000 , the ETH balance from The DAO and it's child DAOs (which includes the balance from the extraBalance account) were transferred into the Withdrawal contract.
Immediately after the hard-fork, at block #1,920,090, the Withdrawal contact's trusteeWithdraw() function was called in this transaction to transfer 463,798.08818109 ETH into TheDAOCurator multisig wallet.
You should be able to find your account that contributed to the Extra Balance account in:
CreatedTokenEventsWithNonZeroExtraBalance_v3.xlsx.
https://github.com/bokkypoobah/TheDAOData/raw/master/CreatedTokenEventsWithNonZeroExtraBalance_v3.xlsx
CreatedTokenEventsWithNonZeroExtraBalance_v3.txt
https://raw.githubusercontent.com/bokkypoobah/TheDAOData/master/CreatedTokenEventsWithNonZeroExtraBalance_v3.txt
If I do not have access to my original account or do not remember the keys?
Sorry for that, but it is your responsibility to have your account and keys on sun safety.
Note:
The curators are currently planning to return your Extra Balance account contributions directly back to your original address.
Make sure that you have access to the original account and passphrase to unlock the account.
Your extraBalance amounts should be correct in the CreatedTokenEventsWithNonZeroExtraBalance_v3.xlsx spreadsheet.
Just be patient as the curators are dealing with the split DAO refunds first as these are a bit more complicated to work out.
What if you buy them through house POLONIEX change?
UPDATE 17:12 24 Jul 2016 AEST
From https://poloniex.com/dao/:
Note: if you created DAO tokens during the crowdsale on Poloniex and paid more than 1 ETH per 100 DAO, you may receive additional ETH in your Poloniex balance in the coming weeks as part of the "extraBalance" refund. This is being handled separately and is contingent on a smart contract being prepared by the DAO and Ethereum teams.
For further information please read this article https://medium.com/edge-cases-multisig-phf-official-channel/the-daos-edge-cases-multisig-post-hard-fork-2f107380bd61#.nwlvtq15d
and/or visit the Slack or the DAOhub forum for further information.
I hope you has been helpful!