ram disk says incorrect function. am i using wrong headers?

i've installed ram disk sample from Microsoft in my target which is
running windows xp professional SP2. when clicked on ramdisk icon, i
get the message incorrect function. when debugged, i found that it
reaches the default case statement in ioctrl function, which returns
STATUS_INVALID_DEVICE_REQUEST.
any idea why would this occur? am i using a wrong header file set?

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