Copy all files to your Tooth Atlas folder. This is usually at 'C:\Program Files\eHuman\3D_Tooth_Atlas_v6' (commonly 'C:\Program Files (x86)\eHuman\3D_Tooth_Atlas_v6' on Vista), however, if you've been told to run this program, this is probably not the case.
To find your Tooth Atlas folder, open the Start Menu, and select 'Programs' or 'All Programs', then go to 'eHuman'. Under 'eHuman', locate '3D Tooth Atlas v6', then inside that item, locate the item also called '3D Tooth Atlas v6'. This last '3D Tooth Atlas v6' item should have a tooth icon next to it. Right-click this item and select 'Properties'. This will brind up the property dialog for this shortcut.
Under the 'Shortcut' tab, you should see a field labeled 'Start in:'. This value is the path to your Tooth Atlas folder, and is where you need to copy all of this program's files to. After copying the files to the Tooth Atlas folder, you should be able to run 'ehregfix.exe' to successfully repair the program's registry entries, allowing it to be located automatically in the future.