Assuming you are using Windows 2000:
Create a new user account (Right click my computer, choose manage), then add that user to the administrators group
Log in as the new user, and change the power settings to how you want them for all users.
Log back in as the administrator. Right click my computer, and choose properties.
Go to the user profiles tab, and highlight the new user profile, and then select copy to. Copy this profile to c:\documents and settings\default user. In the permitted to user section, change to all users.
After you have done this, remember to delete the new user account you just created.
Note: This will only work with NEW profiles, so you would need to delete the profiles on the machine to have the settings take affect.