Try the attached file. I got it off NI's site a while ago. I dont know if it will work for NT but it will for 95, 98. The active button does not mean running. It means if there is a screensaver selected. Choose the set function and set active to false. Then it doesn't matter the time you give it.
Let me know if it works for NT. Make sure the dll its pointing to is the correct place. It uses User32.dll a windows dll.
Jared