Media-class installer rejects install of 64-bit driver on AMD64

I have run into a problem with installing a 64-bit version of a media-class
driver on an AMD64 system with Windows XP Pro 64-bit edition.

The class installer is rejecting the install of the driver.

As you know, for AMD64 in the .inf file you must add the decoration .NTamd64
to the manufacturer information to get the correct identification. This is
described in the document “INF Requirements for 64-bit Systems” at
http://www.microsoft.com/whdc/driver/install/64INF_reqs.mspx

So, instead of:

[Manufacturer]

%XYZMfg%=CompanyName

or:

[Manufacturer]

%XYZMfg%=CompanyName,NT

both of which work on x86 Windows XP 32-bit, you have:

[Manufacturer]

%XYZMfg%=CompanyName,NTamd64

or you can combine them as follows:

[Manufacturer]

%XYZMfg%=CompanyName,NT,NTamd64

I tried all of these combinations on the 64-bit system. With the first two,
the system installer does not recognize a correct combination for the
system. With the last two, the installation is attempted, but the class
installer rejects the install of the driver.

And please note that this “decoration” problem is not specific to the 64-bit
operating system. If I use the decoration .NTx86 on the 32-bit system, this
is also rejected by the class installer, even though it should be correct.
Only the .NT decoration is accepted.

There is a registry setting that will allow an undecorated .inf file to work
on an AMD64 system, but that is not suitable for a end-user installation.

Does anyone know if there is a way to install a media-class driver on AMD64
without running into this problem?

Thanks for any help. If there is another forum on which I should post this
question, please let me know. I have not yet found a 64-bit-specific driver
development forum.