Here is how you do it, I copied this from another site (maybe Microsoft itself?)
Xbox 360: How to use a newly created Xbox 360 Live gamer profile on the original Xbox console
December 7, 2006
Revision 3.3
SUMMARY
This article describes how to use a newly created Xbox Live gamer profile on the original Xbox console after you create the profile on an Xbox 360 console.
MORE INFORMATION
The original Xbox console does not use the same security features for parentally controlled accounts as the Xbox 360 console uses. Therefore, parentally controlled accounts are not backward-compatible. Silver accounts are free accounts and therefore will not work on Xbox Live.
To use your Xbox 360 Xbox Live profile on the original Xbox console, follow these steps:
1.
Before you can use your Xbox Live profile on the original Xbox console, you must enter a minimum set of details in the Xbox 360 console. These required details include your credit card information, your postal code, and your telephone number.
Important If you remove any part of this information from the Xbox 360 console, account recovery will either fail or the account will no longer function on the original Xbox console.
To enter the minimum profile details in the Xbox Dashboard, follow these steps:
a.
Access the account management area in the Xbox Dashboard. For more information about how to access the account management features, click the following article number to view the article in the Microsoft Knowledge Base:
906920 (
http://support.microsoft.com/kb/906920/) Xbox 360: How to access Xbox Live account management features
b.
Select Memberships, and then press the A button.
c.
Select the appropriate membership type, and then press the A button.
d.
Select Change Payment Options, and then press the A button.
e.
Select Add Credit Card, and then press the A button.
f.
Type the name, the credit card type, the credit card number, and the expiration date, select Next, and then press the A button.
g.
Complete the billing address information, and then press the A button.
2.
Perform account recovery on the original Xbox console.
•
If you recover an account, the Xbox 360 Xbox Live account is still valid. You can continue to use the Xbox 360 Xbox Live account after you recover an account on the original Xbox console.
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SECTION 2
Xbox: How to use Xbox Live account recovery
Last Review
:
January 5, 2006
Revision
:
7.3
SUMMARY
This article describes how to use the Account Recovery feature.
MORE INFORMATION
To use the Account Recovery feature:
1.
On the Xbox Live Now Dashboard, press the B button to move to the Select Account screen.
If you are on the Main Menu screen, press the directional pad (D-pad) up or down to select Xbox Live, and then press the A button.
2.
On the Select Account screen, press the D-pad down to select Account Recovery, and then press the A button. You receive the following message:
After Account Recovery, only your account information on this Xbox will be valid.
3.
Press the A button to continue.
4.
On the Account Recovery screen, you must provide your gamertag, credit card information (cardholder name and full credit card number), phone number, and postal code to continue. This is for security purposes.
5.
After you enter your validation information, press the D-pad down to select Continue. When this information is confirmed, your account is downloaded to the Xbox console and you return to the Select Account screen.
Note You must be the primary account holder to use the account recovery process.
If you use this account recovery procedure on an Xbox console other than your own, repeat these steps on your own console the next time you use it to invalidate the use of your account elsewhere.
Note When you download your account to one console, your account is invalidated on any other console during that time. You cannot use one account at two locations at the same time.
