Fro recovering password or user name, go to the following site and use ESO Account Management Tool:

esoaccounts.agecommunity.com
To recover password, type your user name and if you don’t not the username click on Forgot Username option.

If product ID is not known, you might recover the user name situated HDD if haven’t uninstalled it. To find a user name used earlier, go through the following steps:
1. On Windows 7 or Windows Vista, go to Start, and then Documents.
2. Click twice on My Games, double-click Age of Empires 3, and after that double-click on Data.
3. Locate the file, where <account> is the name of your ESO account:
Uipersonastats-<account>.xml
4. Log in ESO.

If unable to find the Uipersonastats-<account >.xml file or password, recover account name via e-mail. Fro using ESO to recover an account name made used for playing send a mail to age3support@robotentertainment.com
With following information:
• e-mail that uses ESO.
• Product ID of copy of Age of Empires III.

After sending e-mail, you will get an automated respond stating request is being processed. If the message is not received an automated response, check Junk Mail folder and Inbox. If still the response is not there, resend the information once again.

An e-mail message with your user name will come back after your request is processed at ESO. It might take couple of days to process.
Retrieve the account password within the game
Using ESO to rearrange an forgotten password go to through following procedure:
1. Double click on Age of Empires III.
2. Select Multiplayer, and then select ES Online.
3. Type user name, and then select Forgot Password.
4. Enter the question provided at the time of sign up for.
5. Press OK.
6. You will receive message regarding the confirmation of proicedure.
7. Press OK.
Follow instructions listed in the e-mail message to recover password.