HW3 is correct but when you've installed the game go into the root folder and right click on the SH3 icon (not any shortcut elsewhere such as on the desktop).
Go to the version tab then click on the file version near the bottom, that will give you a true indication of what version you have.
It looks like your not patched to 1.4b....here is a link to the patches:
http://silenthunteriii.com/uk/updates.php