This phase 2b study will evaluate the efficacy and safety of 16 and 24 weeks of a 4-drug regimen with GS-9451 and Tegobuvir and 24 weeks of a 3-drug regimen of GS-9451 without Tegobuvir, all with Peginterferon Alfa-2a (Pegasys®) and Ribavirin (Copegus®).