Installation Problem

I just installed the game, without upgrading Direct X, and i got a message saying: 'This application has failed to start because d3dx_37.dll was not found. Re-installing the application may fix this problem'. On the demo, when i upgraded Direct X it caused thing like bbc iplayer and windows media player to not work.

1) Is the problem that i didn't install Direct X with the game? (curently have vista)

2) Why did Direct X stop other programs working ?

3) Is the error to do with somthing else

p.s. where do i fill in the keycode, it never asked for it during installation?

edit: solved the problem