Connect that dongle to your computer and register it to your MySteinberg account (this proves that you own it), then try contacting support through there. Studio Case 2 has been unsupported for almost 10 years now though, so I’m unsure if they’ll be able to help you.
Keep in mind that Studio Case 2 is very old and dated, and that it may not work as well as intended on modern OSes. If you were willing to spend money I think it would be a better idea to just buy him Cubase Elements 8. It comes with replacements for most of Studio Case’s content:
-Cubase Elements 8 is much better and more accessible than Cubase SE3. There’s also far more guides and tutorials for it on YouTube.
-Groove Agent SE 4 sounds a million times better than Groove Agent SE. Comes with a solid acoustic drum kit and several synth drums.
-Prologue isn’t as deep as D’cota, but it should be more than enough for a newbie.
-Halion Sonic SE 2 is missing most of the content from Cubase Artist and Pro, but it still has decent versions of the most important General MIDI sounds.
Cubase Elements doesn’t come with anything like Virtual Guitarist though. If he’s a rock guy you would have to get something like Ujam’s Virtual Guitarist Iron.