When you went into "Control Panel" and then "Programs and Features" (or whatever it is called in Vista) and then click on "View Installed Updates" it is not showing up there as MDAC?
Actually from what I have read on it, it should have already been included or installed as long as you had I.E. 5 or newer installed, so you may have had or still have some other issue going on.
ASUS Maximus V Gene MB
Windows 8 X64; Windows 7 X64; Windows 7 X86
16GB Corsair Vengeance Ram
eVGA GeForce GTX 550 TI
Corsair GS700 PS
1TB Seagate SATA 6.0Gb HD