  The conformal thermodynamics of rotating charged black holes in general
relativity and string theory is proposed by considering the first laws of
thermodynamics for a pair of systems made up of the two horizons of a
Kerr-Newman or Kerr-Sen black hole. These two systems are constructed by only
demanding their ``horizon areas'' to be the sum and difference of that of the
outer and inner horizons of their prototype. The thermodynamics present here is
a ``conformal version'' of black hole thermodynamics, since it is closely
related to the near-horizon conformal symmetry of black holes. The concept of
non-quasinormal modes recently proposed by D. Birmingham and S. Carlip [9] is
compatible with this ``conformal thermodynamics'', rather than the usual
``horizon thermodynamics''. In addition, we show that this conformal
thermodynamics resembles to the thermodynamics of effective string or D-brane
models, since the two newly-constructed systems bear a striking resemblance to
the right- and left-movers in string theory and D-brane physics.
