when hiro went back to 1671 adam was locked up by the company.
so how does he remember hiro?
this whole time travelling thing is confusing

assuming all of past-present-future is related, whatever happens then, dictates what happens now, so in essence he changed the future, or, that was supposed to happen, and it is just history following its course...?

from Adam's POV:
Born and lived in the 1600s. Some dude from the future comes back in time and tells you you are supposed to be a hero. You find out you heal. You fall in love, dude from future takes your love. Etc etc. Camp blows up, you regenerate, and continue living. Cut forward 400 years. You join up with 12 folks to start the Company. Eventually they hold you prisoner. You befriend Peter, he helps you escape. You go to Primatech and bam, look, it's that dude from the future again. "Hiro?!"

Adam hasn't done any time-traveling.

Because Adam was alive and "free" in 1671 and he met Hiro then.

Let's say it's like this:

1671 w/o Hiro, Adam was a conman so he's supposed to be bad already --- lived 400 years ---- met the 12 ---- 1977 locked by kaito, doesnt know Hiro yet ---- kaito had son Hiro ----- Hiro goes back to 1671 to change adam ---- 1671 with Hiro, Adam still became a bad guy w/ Hiro knowledge already ---- lived 400 years ---- met the 12 ---- 1977 locked by Kaito, knew Hiro but doesn't know where hiro is ---- met Hiro at Primatech, recognized him.

This is Hiro's timeline, based on his time travel. So either with or without Hiro, Adam is still a villain. When he was preaching to the 12 members, he told them what his intentions were, and it was nothing like: "because I loved a girl in 1671 and was betrayed by a friend (hiro)." His intentions were: "to end humanity and become a hero."

But in 1671, he vowed that everything Hiro loved will be led to waste. So in that time, that was his intention. But imagine living for 400 years! He went thru world war 1, 2, the holocaust, famine, tsunami, earthquakes, man's disregard for the environment... imagine having to go through all of that, it will make you want to end the world as well. LOL. So maybe his thinking was a little bit "crazy" already. In the graphic novel, in the 18th cent, he said, "I was alone." so imagine that, people around you dying and you lived through all of those tragedies?