Another way, is to access the user accounts via Control panel, User accounts. Then click on "Change the way users log off and on"
Next Uncheck "Use the welcome screen".
Now, you have to type in the user name and password. No more of this click the user name thing.
Also, to clear the previous logged on username from showing up, simply do the following.....
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon
DontDisplayLastUserName REG_SZ
Range: 0 or 1
Default: 0 (false)
By default, Windows NT displays the name of the last person to log on in the Username space of the Logon Information dialog box. If you add this value entry and set it to 1, the Username space is always blank when the Logon Information dialog box appears.