SetupCopyOemInf on non WHQL USB drivers

Hi,
I have written a simple application that runs to preinstall driver for the Windows XP such that if you plug in the device, the Add New Hardware Window would not appear.

I am able to perform this successfully when my driver has a valid catalog file, which means it is WHQL certifed.

But for non-WHQL certified drivers, I cannot seem to make this work. When I run SetupCopyOemInf, it always returns TRUE, which means the inf was successfully pre-installed. But when I plugged in the device, the Add New Hardware Window still appears.

So my question is, why does SetupCopyOEMInf return true even with drivers having no WHQL certification/ valid catalog file yet when you plug in the device, the Add New Hardware Window still appears?

thanks,
-Fred

/*in this case, result returns 1 (TRUE)*/
/*infPath points to the inf file path*/
/*execPath points to the path of where the inf is contained*/
 
result = SetupCopyOEMInf(
        infPath,
        execPath,
        SPOST_PATH,
        SP_COPY_NOOVERWRITE ,
        destFilename,
        requiredSize,
        &requiredSize,
        NULL
    );

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