If you want to hide users, try this approach:
To hide additional user accounts on Windows & Logon Use Regedit, also works for Vista
Hide User Accounts in windows Vista and Windows 7
At Run, type regedit
Once in regedit go to HKEY_LOCAL_MACHINE\Software\Microsoft\WindowsNT\CurrentVersion\Winlogon
In the left panel, right click on Winlogon and click New and click Key.
Type SpecialAccounts and press Enter
In the left panel, right click on SpecialAccounts and click New and click Key.
Type UserList and press Enter.
In right panel of UserList, right click on a 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.eg: Everyday Account.
In the right panel, right click on the user account name and click Modify.
To hide the user account – Type 0 and click OK. (number zero not the letter)
Whenever you want to use the account just unhide the it by typing 1 instead of zero.
This process is described in more detail here.
As an alternative, you can hide the entire Welcome Screen and force everyone to enter their Username and Password as described here. The registry value should be set to 1.