Start -> Run:
type regedit
then navigate to:

Hkey_Local_Machine\Software\Microsoft\WindowsNT\CurrentVersion\Winlogon. In the left pane, right click on Winlogon and click New and click Key.
Type “SpecialAccounts” and press Enter.

In the left pane, right click on SpecialAccounts and click New and click Key.
Type “UserList” and press Enter.

In right pane of UserList, right click on an empty area and click New then click DWORD (32bit) Value.
Type in the name of the user account that you want to hide and press Enter .e.g.: “IT”.

In the right panel, right click on the user account name and click Modify.

To hide the user account – Type ”0″ and click OK. (The number zero not the letter O). Changing this value to “1″ will unhide the account.

user account · vista · windows 7