You don't need to mess with the registry to do this.
1. Click Control Panel
2. Click Power Options
3. Select the Hibernate tab
4. Uncheck Enable Hibernation box to disable
(or check to enable)
5. Click OK

Disabling startup login prompt for password
Click Start and Run
Type "Control Userpasswords2" and press enter.
Uncheck the box for "Users must enter a user name and password to use this computer."
Click Apply and Ok.

Disabling prompt for password after Windows XP resumes from standby or hibernation
Click Start, Settings, and Control Panel
Double-click Power Options
Uncheck the "Prompt for password when computer resumes from standby" option.
Click Apply and then Ok.