typedef LARGE_INTEGER LUID
A Locally Unique Identifier, or LUID, is a value that is guaranteed to be unique on only the system it was generated on. Furthermore, this uniqueness is only guaranteed until the next time the system is re-booted. That is, LUIDs are not unique across boots.
LUID is declared as type LARGE_INTEGER, but it should be treated as an opaque structure.
LUID_AND_ATTRIBUTES