Direct X and older games

I have bought a copy of fear, which is a couple of years old now obviously but when I goto install it I am asked to install the older version of direct x 9 (I have 10 on my computer) if I install this will it impact my other games or will I simply need to install the latest version of 10 after?

Thanks guys (yes pc noob, im from the days when dvd rom was an extravagance!)