Return of the king installation problems

[Legolasforever]

I can't install my version of Return of the king on my system (1.8Ghz, 64Mb video, 512 Ram, DirectX9.0 , windows XP). I can only do two steps during installation, clicking on the "install" option on the start screen and clicking Yes on the users'licence agreement. then there seems to be an error with CDkey, it always flips so I cant insert my cd key.

plz help me , cz I love LOTR and I am really eager to play the game.

thx

Pieter