By default the nsthdinstall will NOT install a boot loader. If your system already has a boot loader, you will need to edit its configuration file to add the NST partition as one of its boot options.
If you include the --grub-install
option when you invoke nsthdinstall, it will install a
boot loader for you. HOWEVER, this will become the default
boot loader for your system and you will need to edit the
/boot/grub/grub.conf file if you wish to
boot any other operating systems on your hard disk.