  It is well-known that del Pezzo surfaces of degree $9-n$ one-to-one
correspond to flat $E_n$ bundles over an elliptic curve. In this paper, we
construct $ADE$ bundles over a broader class of rational surfaces which we call
$ADE$ surfaces, and extend the above correspondence to all flat $G$ bundles
over an elliptic curve, where $G$ is any simply laced, simple, compact and
simply-connected Lie group. In the sequel, we will construct $G$ bundles for
non-simply laced Lie group $G$ over these rational surfaces, and extend the
above correspondence to non-simply laced cases.
