Catching up on forumming
You are welcome but it's the community in general that's still with it.
RE: hacking, well, no, if you play AOE2 HD on Steam or with the user patches on Voobly, I have almost forgotten what life was like when every other game was being hacked (e.g., the map hacking where people's fog of war was lifted or the resign hacking where you would force another person from resigning) because there are strong anti-cheat/anti-hack measures in play now.
I don't see how your OS would prevent you from joining a game on Steam, but wouldn't a 15 year old computer have crappy specs? I would be worried about graphic cards designed for the good old days of 1024x768 gaming not keeping up with AoE2HD in 1920x1080.
Tutorials are available all over the place like YouTube. There are many streams on Twitch. Recorded games are abundant. e.g., this website has tons of old recs from previous tournaments.
So, again, it's pretty much Steam and Voobly.