  The evolution of C and O abundances in the Milky Way can impose strong
constraints on stellar nucleosynthesis and help understanding the formation and
evolution of our Galaxy. The aim is to review the measured C and O abundances
in the disk and bulge of the Galaxy and compare them with model predictions. We
adopt two successful chemical evolution models for the bulge and the disk,
which assume the same nucleosynthesis prescriptions but different histories of
star formation. The data show a clear distinction between the trend of [C/O] in
the thick and thin Galactic disks, while the thick disk and bulge trends are
indistinguishable with a large (>0.5 dex) increase in the C/O ratio in the
range from -0.1 to +0.4 dex for [O/H]. In our models we consider yields from
massive stars with and without the inclusion of metallicity-dependent stellar
winds. The observed increase in the [C/O] ratio with metallicity in the bulge
and thick disk lies between the predictions utilizing the mass-loss rates of
Maeder (1992) and those of Meynet & Maeder (2002). A model without
metallicity-dependent yields completely fails to match the observations. Thus,
the relative increase in carbon abundance at high metallicity appears to be due
to metallicity-dependent stellar winds in massive stars. These results also
explain the steep decline of the [O/Fe] ratio with [Fe/H] in the Galactic
bulge, while the [Mg/Fe] ratio is enhanced at all [Fe/H]. (abridged)
