NO SOUND (DirectX Issue)

Well, ive been working on this for a good 2 days, over 14 hours of looking for solutions, uninstalling serveral programs and reinstalling and still have no solution. Black ops works fine, everything except my sound. When I go into black ops, and try to change my device, its blanked (greyed) out and unable to change it. It's set to stereo speakers (my default device is realtek HD audio) and currently I have no speakers (im using headset). I know for a fact its a DirectX error because my DXSETUP in my black ops redist folder does not work, the installation ALWAYS fails even from the microsoft website. Please, if you have any ideas, help me out.

-EDIT: When I try to install the missing parts with DXSETUP it stays at initializing, then copying files, without the bar loading at all. Then it shows d3dx9_24.dll in text below the bar, the bar loads, and a message pops up saying "DirectX Setup" and after I say ok, the installation ends saying "installation failed". I've tried downloading d3dx9_24.dll and putting it in redists, but it doesnt help. Also quick note, when I first bought the game, it wouldnt boot up, wouldnt load or anything, and I dowloaded d3dx9_43.dll, put it in the black ops folder, and it works. so that just shows I have missing parts despite the fact that I have up to date DirectX and it says theres no broken parts in it.