The game has to be run out of its installation folder. During the installation you can chose where to install it. You cannot copy the game to another folder and run it, without having problems.
If you want to move the game, the best way to do it is;
1) Remove the current installation using the Add/Remove Programs ICON in the Windows Control Panel. Do not worry, this does not remove any of your settings for the game.
2) Install the game in its new location.
3) Navigate to the original installation folder and copy the 'settings', 'ahiiterr', and 'skins' folders to the new installation folder. You can them remove the original HTC installation folder.
That should take care of it.