I just had a quick look at my registry and the path for the WinNT/W2K system services is:
A good example of a W2K System Service which uses it's own executable is e.g. Telnet (TlntSvr).
Have a look at the structure and you should be able to put up a new service with NSIS.
For more information about Winows System Services goto:
and search for system services.
I'm not sure what you mean by "hide sections based on string values". If you mean that you would like to create a section which does not show up in the install-options just create a Section called "".
If you need to detect the Windows Version of a system I recommend the following address: