Hm... it seems you already have the latest version which is 1.4 donloaded via steam. But to make sure you should make a right mouse click on your sh3.exe file and compare with my picture:
If you have version 1.4, apply the no dvd thing to avoid copy protection issues.
Then try to start the game!
If it still won´t work, try to use the Vista/Win7 Patch for WAC.
greetings
Han