Downloaded windows DX9 update today and it turned my PC into a pig of a machine!! Instead of acting like a dream machine (£ mths old) it was pretending to be about 50yrs old, and seizing up and taking repeated clicks of mouse for any command to be recognised. Have uninstalled it now and seems to be ok again (fingers crossed!)
The above refer to Knowlege base articles 819696 (MS03-030: Unchecked Buffer in DirectX Could Enable System Compromise) and 829778 (Security update for Windows (819696) is re-offered even though DirectX 9.0b is installed)
Go here click here then enter the article number and search this will bring up the correct pages.