At our office we have special software in which we can create users. Once the software is running completely, the users created in our software are automatically created in Windows. They belong to the restricted users group, so that means that they are not able to change the Power options in control panel. The only thing that bothers me is that, by default, the power scheme is set at "Home/Office Desk" which means that the monitor will be turned off after 20 minutes of non-activity. I have noticed that the "Presentation" scheme leaves the monitor on at all times, and that's exactly what I want. Is there anybody who knows how I can change the registry (or write a script for that matter) so that every newly created user has the "presentation" scheme? Or maybe how the setting for the monitor can be changed in the "Home/Office Desk" into "Never", of course again for every newly created user...

There are two types of answers for that. One answer is for if it is a network of computers you are talking about and the other answer is for if it is just an individual computer without the use of a network. For now I will call the type of user account that has limited permissions a 'standard user' and the type of account that has full permissions 'admin'.

So if it is a network then try the following:
Set up a new standard user account then in admin, give that one user account enough permissions to change the power settings (without changing the type of account). Then if that standard user changes the power settings it should effect all users but you will need to get that new standard user account to change the settings on each individual computer. After the new standard user has changed the settings you can delete that new user

If it is a single computer not connected to a Local Area Network then try the following:
If it is just a single computer (eg. xp home login) then you will need to first turn all standard user accounts into admin accounts. Then get each user to change the power settings then you can change all those users back to standard user accounts. But all these settings and account alterations would be done through the control panel.

As for making an account to by default have those settings being pre-changed, you would probably need to find an extension to the program you are using to create the accounts or to find a windows hack for it.