Figured out the way: it's not your user log-in. It's an LDAP DN like:
CN=My Name,OU=My Company,DC=server,DC=local
To prepare the forest and domain for the installation of the first Windows Server 2008 R2 domain controller please perform these tasks:
Lamer note: The following tasks are required ONLY before adding the first Windows Server 2008 R2 domain controller. If you plan on simply joining a Windows Server 2008 R2 Server to the domain and configuring as a regular member server, none of the following tasks are required.
Another lamer note: Please make sure you read the system requirements for Windows Server 2008 R2. For example, you cannot join a Windows Server 2008 R2 server to a Windows NT 4.0 domain, not can it participate as a domain controller in a mixed domain. If any domain controllers in the forest are running Windows 2000 Server, they must be running Service Pack 4 (SP4).
First, you should review and understand the schema updates and other changes that ADPREP makes as part of the schema management process in Active Directory Domain Services (AD DS). You should test the ADPREP schema updates in a lab environment to ensure that they will not conflict with any applications that run in your environment.
You must make a system state backup for your domain controllers, including the schema master and at least one other domain controller from each domain in the forest (you do have backups, don't you?).
Also, make sure that you can log on to the schema master with an account that has sufficient credentials to run adprep /forestprep. You must be a member of the Schema Admins group, the Enterprise Admins group, and the Domain Admins group of the domain that hosts the schema master, which is, by default, the forest root domain.
Next, insert the Windows Server 2008 R2 DVD media into your DVD drive. Note that if you do not have the media handy, you may use the evaluation version that is available to download from Microsoft's website. You can also use an MSDN or Technet ISO image, if you have a subscription to one of them.
http://www.lepide.com/active-directory-management-and-reporting.html
Best Answer
Is PowerShell an option? If so you can do something along the following.
Get-ADUser USERNAME -Properties * | Select SamaccountName,ObjectSid,ObjectGUID