  We have tested the two main theoretical models of bubbles around massive star
clusters, Castor et al. and Chevalier & Clegg, against observations of the well
studied Carina Nebula. The Castor et al. theory over-predicts the X-ray
luminosity in the Carina bubble by a factor of 60 and expands too rapidly, by a
factor of 4; if the correct radius and age are used, the predicted X-ray
luminosity is even larger. In contrast, the Chevalier & Clegg model
under-predicts the X-ray luminosity by a factor of 10. We modify the Castor et
al. theory to take into account lower stellar wind mass loss rates, radiation
pressure, gravity, and escape of or energy loss from the hot shocked gas. We
argue that energy is advected rather than radiated from the bubble. We
undertake a parameter study for reduced stellar mass loss rates and for various
leakage rates and are able to find viable models. The X-ray surface brightness
in Carina is highest close to the bubble wall, which is consistent with
conductive evaporation from cold clouds. The picture that emerges is one in
which the hot gas pressure is far below that found by dividing the
time-integrated wind luminosity by the bubble volume; rather, the pressure in
the hot gas is set by pressure equilibrium with the photoionized gas at T=10^4
K. It follows that the shocked stellar winds are not dynamically important in
forming the bubbles.
