You do realize that Windows Defender is in Beta, don't you Shady? If it isn't, boy are they talking about this product on hacker/security sites. What is happening with Microsoft? Nobody can touch you, you're the leader of the pack, and why do you have to be sneaky about anything at all? You'd do better to tell us all the truth about everything affecting your millions (maybe trillions) of customers!
So, to help you a little bit, Shady, because I know how frustrating it is to find help from Microsoft without reading a thousand different links or paying for it, 64x indicates you're trying to install a Windows XP 64-bit version of Windows Defender. If you have Windows XP Home or Windows XP Professional, they are NOT 64-bit Operating Systems. If you really want that thing on your computer, you need to find the one for the Windows XP version that you have. I don't know anybody, personally, that has Windows XP 64-bit on their computer; I think it's tainted towards businesses; and it is an easy mistake to make.