   How many PCs have directX9
  How many PC users have directX9 and how many dont?I ask this to know if I should write an application in directX9 or write it in a some other windows API.Thanks in advance.   
  That is a difficult question to answer but the closest you'll get to a real answer is checking out the steam survey results here Steam Survey Resultshope that helps.   ;  I'm betting you're looking for a percentage, not an actual number.WindowsXP SP2 shipped with DX9c, IIRC. You could safely assume that anyone with SP2 has it, and anyone without it pretty much doesn't (If they don't bother installing the SP, they won't bother installing DX). You should be able find statistics of installation of SP2 on the MS site, and they are pretty high. I'm guessing somewhere around 95% or higher.Hope this helps :).   ;  I think it is safe to assume that those people who plan on playing your game will play other games and probably have directx already set up. The people without Directx 9.0c have versions before XP SP2 are rpobably not your target audience anyways.   