I had this same problem. My computer has a 64 bit processor and came with
Vista Home Premium (32 bit) already installed. Windows Security Center
recognized every security program I evaluated. I then reformatted my hard
drive and did a clean install upgrade to Vista Ultimate (64 bit). I had to do
a clean install because you cannot update a 64 bit OS over a 32 bit OS.
Windows Security Center recognized all security software I evaluated on it.
However, the lack of 64 bit software applications forced me to go with the
Vista Ultimate 32 bit. I reformatted my hard drive and did a clean install of
Vista Ultimate 32 bit. Windows Security Center WOULD NOT recognize any
security software, not even Windows Defender and Windows Live One Care. I
know they were operating properly because I watched them in Process Explorer
and Task Manager. The software also properly updated itself. Windows Security
Center would not recognize the software even after I ran the software and
rebooted several times. I then called Microsoft. I talked with them for appx.
one hour before they finally made the decision to close the case as unsolved.
I then reformatted my hard drive once again, reinstalled the OEM Vista Home
Premium and upgraded to Vista Ultimate 32 bit. I don't know why but the
problem has been solved. Windows Security Center now recognizes any and all
security software installed and running. However, please be advised that if
you install Windows Live One Care it will disable Windows Defender as Windows
Defender has been "incorporated" into Live Once Care. The good part in all of
this is that it takes me only 15 minutes to do a clean install of any of the
Vista operating systems and only 20 minutes for the upgrade. I don't know why
this is so. I don't have a superfast computer. I am running an AMD Athlon x64
4200 dual core processor on a Dell E-521 desktop, 320 GB hard drive, 2 GB of
dual channel memory and an ATI Radeon x1300 pro graphics card. As you can
see, this system is nothing special.