We study the effects of WIMP dark matter (DM) annihilations on the collapse 
and
evolution of the first stars in the Universe.
First, we use a 1-D hydrodynamical code to study the final phases of the 
protostellar
collapse, exploring the parameter space in order to determine whether the 
energy
input from annihilations can modify the star formation process.
Then, we use a stellar evolution code to follow the pre-Main Sequence (MS) 
phase of a
grid of metal-free stars, looking for the effects of the DM energy input on their
evolutionary tracks.
In our calculations we account for adiabatic contraction and scattering/capture
processes.
Such processes can enhance the central DM density so much that the 
annihilations can
effectively counteract the gravitational collapse: in some instances the protostar 
is
prevented from reaching the ZAMS, while in other cases the changes (e.g., a 
doubling
of the MS life) are less dramatic.