I need to know how to change the "Default Logon" username/domain

I need to know how to change the "Default Logon" setting so that when I get
done doing a security check on a users work station I can reset the login to
their domain\username not the one I used to access their system, there by
masking my having logged in on their PC in the first place. In XP I had a
registry hack I could run...

REGEDIT4

[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon]
"DefaultUserName"="UserName"
"DefaultDomainName"="DomainName"
"CachePrimaryDomain"="DomainName"

What ever name and domain I put in the reg hack, that would be the default
name/domain that would show up at the login prompt in XP. Vista has these
same settings in the registry, but setting them does not change the log in
prompt to the desired domain\user, it leaves it set to the last one to log
on. Needless to say this is a very important thing for IT admins to be able
to control, so how do I get control in Vista and Windows 7? (We use Windows
7 Enterprise x86 and 64 bit) I need a one click option like the one I can use
in XP, shown above, for Vista and Win 7 which will let me change the
domain\username prompt.

Microsoft, please advise,

Ralph Malph

PS.. I can find a Windows Vista section, but no Windows 7 for posting these
types of questions.....