Thanks to Katuko's link, I played the game and can provide a review:
I am very confused.
I can use the arrow keys to move Tahu, but it's Pac-Man style controls - once I press an arrow key one way, Tahu will continue moving in that direction until he hits an obstacle or I press another arrow key - typically for top-down games, players will expect more traditional controls where Tahu will not move if no key is being pressed.
If Tahu touches the blue thing on the top-right corner of the screen, the game just stops. I assume that means I died?
After a long time of randomly clicking things (Edit: I realize now that you described it in the opening post, but I was too confused by that post's missing download link to read further) I found out that if I click on the hut, an "MT" button (I assume that stands for "Matoran") appears in the top left of the screen. If I click that, a Matoran appears there, but he can't move - I'd expect to be able to select him like in Age of Empires and other similar games. Similarly, the... building... thing that Vakama is standing on seems to produce a "Toa" button, which spawns a clone of Tahu. This has a rather amusing side effect: all Tahus on screen will respond to the arrow keys. Interestingly, if any Tahu touches an enemy, they all disappear. If any Tahu touches the Deadly Blue Thing, the game exits.
Then there's some bugs. There's some Bohrok near the wall... but after a few moments, they seem to disappear. I can't seem to make this happen consistently, though. The Rahkshi pace back and forth menacingly at the beginning of the game, but then they retreat to the left side of the screen and stop moving. If I "glide" over to the wall, I'll stop, but if I hold down the arrow key, I'll phase right through it.
You've clearly got the beginnings of a strategy game here, but honestly, I would have worked a bit more on it before posting it here. If you wanted to post a topic, some screenshots would have worked to show the essence of the game, perhaps even better than an unfinished demo.
Also, I'm playing it with no difficulties (besides the ones described) on Windows 8. Why are you so insistent that it only works on XP?