This game was released in a similar fashion to the release of previous minigames by FireFly Studios with the purpose of promoting the upcoming game of Stronghold 2.
"Defend your castle against hordes of marauding enemy spearmen, nail the catapult before it obliterates your castle walls and use your flaming logs to repel the deadly axemen!"
Anyone that can play Stronghold 2 has a computer that can definitely play this game, a few older ones may be able to as well.
This game has been split into to files. Both must be downloaded. Extract the contents of the zip file to the same location. Then, extract the .rar files using a program that can handle them. I recommend using the FOSS program 7-zip or the freeware program WinRAR.