The installation could fail if;
1) You ever did a restore point in Windows. Only resolution is to do a full installation of the game.
2) If the game is not located where it was intially installed on the computer hard drive. Either move it back to the initially installed location, or install the full version of the game. Before installing, be sure to run the de-installer in the Windows Add/Remove Programs ICON.
There could be other reasons. But those are the most prominen.