Why does user logon screen come up after standby mode in XP

From a security perspective, XP Pro should prompt for your password when coming off standby or hibernation mode. But if your workstation is at home or in a very secured location, to disable this important security feature:
Start the Power Options Control Panel applet
Start.
Control Panel.
Power Options.
Select the Advanced tab.
Uncheck the Prompt for password when computer goes off standby check box.
Click OK.