>Type secpol.msc in Vista's Start Menu Search Bar and hit Enter. This will open the Local Security Policy editor.
Navigate to Security Settings > Local Policies > Security Options. 

![alt text][1]

>Now on RHS, look for Interactive Logon: Hide last username
Rt click on it and open its Properties.
Set it to Enabled > Apply.

![alt text][2]

[source][3]


  [1]: http://www.winvistaclub.com/image/clog1.jpg
  [2]: http://www.winvistaclub.com/image/clog2.jpg
  [3]: http://www.winvistaclub.com/t47.html