  Using a code that employs a self-consistent method for computing the effects
of photoionization on circumstellar gas dynamics, we model the formation of
wind-driven nebulae around massive Wolf-Rayet (W-R) stars. Our algorithm
incorporates a simplified model of the photo-ionization source, computes the
fractional ionization of hydrogen due to the photoionizing flux and
recombination, and determines self-consistently the energy balance due to
ionization, photo-heating and radiative cooling. We take into account changes
in stellar properties and mass-loss over the star's evolution. Our
multi-dimensional simulations clearly reveal the presence of strong ionization
front instabilities. Using various X-ray emission models, and abundances
consistent with those derived for W-R nebulae, we compute the X-ray flux and
spectra from our wind bubble models. We show the evolution of the X-ray
spectral features with time over the evolution of the star, taking the
absorption of the X-rays by the ionized bubble into account. Our simulated
X-ray spectra compare reasonably well with observed spectra of Wolf-Rayet
bubbles. They suggest that X-ray nebulae around massive stars may not be easily
detectable, consistent with observations.
