Divx is not really needed to play the game, just for the intro movie - that can be disabled without problems - so you do not need to install Divx
. If you want it, simply go to the DivX page (http://www.divx.com/)
and install the latest player and codec pack), and ignore the version that the WW1 game installer propose.
As to Directx9, Win7 and 8 indeed ship with newer versions of directx than the "old" 9, true. But many "old" (and some not that old) require the original directx9 drivers to be installed in your computer, side by side with the newer directx.
This is absolutely safe and normal to do for a gamer, and it won't absolutely mess with anything in your windows or other games. The safest way is to download it directly from Microsoft:
Then you will be set to go and can also ignore the option to install it via the WW1 game installer.
Other usual sugestions if you still have problems are to disable UAC (first thing I do with my Windows), and be sure that your game folder in it's entirety is exempt from your antivirus real-time scanning
(PS: WW1 gold use a completely different engine from all other Ageod games (from BoA to AJE/BOR), so eventual problems you may find in WW1 have nothing in common with the other Ageod games)