Windows 7: dxgi.dll missing when launching Windows Live Messenger and DXDIAG.exe

On Sun 27/01/13, I found that Windows Live Messenger was displaying an error:- msnmsgr.exe System Error - The program can't start because dxgi.dll is missing from your computer. Try reinstalling the program to fix this problem.
I also discovered that IE9 32bit and Skype were displaying blank screens. IE9 64bit was working ok. A Thread suggested that I run DXDIAG.EXE to establish if DirectX was working. On running it, it also displayed the error listed above.

File dxgi.dll DOES exist on my laptop in :-
C:\Windows\System32. C:\Windows\winsxs\amd64-microsoft-windows-directx-dxgi....4409,
C:\Windows\winsxs\x86-microsoft-windows-directx-dxgi....d2d3,
C:\Windows\winsxs\amd64-microsoft-windows-directx-dxgi....c06f,
C:\Windows\winsxs\x86-microsoft-windows-directx-dxgi....4f39.

I reinstalled Windows Live Essentials and Skype - no change.
I System Restored to a point on 25/01/13 before the errors occurred- no change
I System Restored to a point when I last used Skype successfully on 17/01/13 - no change

Skype support says that their latest versions use Internet Explorer 32bit and DirectX. So I uninstalled IE9 and I now have the previous version IE8. Skype and IE8 32bit now work ok, but I still get the same dxgi.dll messages when I try to run WLM and DXDIAG.exe.

I don't need to use WLM as MS have migrated to Skype. But I am concerned why these messages are occuring and also that there may be a corruption with DirectX.

Any suggestions?

Thanks