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.