Click on Start and then enter the following command in the search box:
netplwiz
Press the ENTER key.
This command will load the Advanced User Accounts Control Panel applet.
• In the Users tab, check the box next to Users must enter a user name and password to use this computer.
• Click on the Apply button at the bottom of the User Accounts window.
• When the Automatically Log On dialog box appears, enter the user name you wish to automatically login to Windows 7 with. Then enter your account password in the two fields where it's asked.
THE PASSWORD IS NOT REQUIRED!!!
Leave blank if no password exists.
Click the OK button.
I have this setup for a Windows 7 box with 5 user accounts on it.
In my case,as an example why someone would setup something like this...
This is for my Media Center. 99% of the time the sole purpose of powering up the box is to launch XBMC.
Current setup is, power up the box...it automatically logs in to the account and launches XBMC app.
I have an account that is strictly for XBMC while other accounts may occasionally login (Immediate family) so that they can access their own private resources across the homegroup from either the living room TV or remote desktop via laptop or other PC.