A Note on the Geometry of CHL Heterotic Strings

We present a few remarks on disconnected components of the moduli space of heterotic string compactifications on $T_2$. We show in particular how the eight dimensional CHL heterotic string can be understood in terms of topologically non-trivial $E_8\times E_8$ and $\Spin(32)/Z_2$ vector bundles over the torus, and that the respective moduli spaces coincide.