If you want to disable Help from the Start Menu (say as part of a kiosk setup), there is no registry hack to do this. The help file opened when Start\Help is clicked is %SystemRoot%\System32\Windows.hlp. One solution is to delete that file or restrict access (assuming NTFS). Both cases result in error messages. A better solution is to replace the windows.hlp file with the Zero Administration Kit Zak.hlp file. Replacing Windows.hlp with a renamed zak.hlp will result in the following text being displayed when Start\Help is clicked:

Help Topics: Zero Administration Kit Help

The only topic on which you can get help is "ZAK Help." Double-clicking this topic results in the following message:

Zero Administration Kit Message

The standard Windows NT 4.0 online Help has been disabled by your
administrator.