Those that own a legal copy of Stronghold or Stronghold Crusader can update their game to the HD version.
How to do this? (taken from Firefly’s Facebook wall).
1) Go to one of our Stronghold HD websites: These are www.strongholdhd.com and www.strongholdcrusaderhd.com
2) Click on the orange “Download Patch” button
3) Pick your download mirror
4) Download and run the patch
Reading some comments there, it looks like some fans are saying that they can’t apply the patch on their old Stronghold copies. The best thing to do is to buy the games or one of them from GOG.com. I was able to find Stronghold Crusader HD that costs 7,99$, here.
What the HD version brings new?
The games are available in high resolutions. You can actually view the entire map without having to scroll. New units and missions.
The graphic is the same, it is using the same old graphic engine.