Limit automatic login in Vista by number of boots
It's possible to limit the automatic login feature, so that the Log On dialog (or Welcome screen) reappears after a specified number of boots.
1) Open the Registry Editor.
2) Expand the branches to HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon. (Note the Windows NT branch here, as opposed to the more common Windows branch.)
3) Create a new DWORD value here by going to Edit → New → DWORD (32-bit) Value, and type AutoLogonCount for the name of the new value.
4) Double-click the new AutoLogonCount value, and type the number of system boots for which you'd like the automatic login to remain active.
Every successive time Windows starts, it will decrease this value by one. When the value is zero, the username and password entered at the beginning of this topic are forgotten, and the AutoLogonCount value is removed.
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