Direct X Is Installed but not installed

Hey Guys Ummmm MY Direct X come with windows 7 right?
so when i open the direct x identification window it says direct x 11 is installed...
but every application game or browser that requires direct x says it isn't even installed and i play alot of games and non of them work and the common message is "please install DirectX V.8.1 or above" it means that i doesn't even sees the directx and i tried to install it from the web and i install it normally but it's like nothing happens???!!
i dont know how to get the computer specs but it's a Dell Inspiron 1520
operating system Windows 7 Ultimate 64bit

You might want to try to download the latest version from MS. It is possible the direct X on your PC is corrupt.

I downloaded it but when i extracted it it gave me a powerpoint file and a .wav file

Some games need DirectX of an earlier version. Since DirectX 11 is the newest, and not all video cards can even run it, there may be a problem. I think you can download DirectX 9.0c which might be what you need. Many games will install their version of DirectX, if they are allowed.

Try running the dxdiag.exe program, and make note there is an option to run the x64 version on the page.