Since you found this thread, i'm going to assume you've tried to start up a game, and for some reason its telling you that you're missing some files. Most likely they're vaguely named, but you narrowed it down to missing DirectX files of some sort. Some examples could be: d3dx9_24.dll D3DX9_43.dll d3dx10_38.dll d3dx11_43.dll Those are all DirectX file names, taken from my system as i wrote this thread. Note how they mention what versions of DirectX they are for, and a 'version' number. This number is important, because Microsoft regularly updates DirectX. Where people get confused, is they think that by having directX 11 installed it means that have DirectX 9 and 10 installed and up to date as well - but Microsoft continue releasing updates for DX9 and 10 even though DirectX 11 was released long ago. Just because you have DX11, doesn't mean you have directX 9.0C 'version' 43 (D3DX9_43.dll) Normally the game would ask to install/update its required DirectX version when its installed, and that's why people don't have this problem often. Right now you are probably thinking a variant of "Oh yeah, i installed this game on another copy of windows, and restored it from a backup/other hard drive without reinstalling" as it all clicks into place. Microsoft have a generic installer/updater for DirectX that updates all versions of DirectX - DX9/10/11 all at once) - but for some reason its usually labelled as a 9.0c installer, and NOT on windows update. The Web Updater (which requires an internet connection to work) is located HERE. This version is recommended if you just want to updated the one machine. If you want/need to update several machines, or have craptastic internet - you want the Redistributable version, found HERE To note just how bad microsoft are at this, look at this image. DirectX from June 2010 released on the 18th of April 2011 Feel free to leave questions or comments, thanks are best done by clicking the thanks button so we dont clog up the thread.