Patients may enroll in 1 or none of the following substudies: A5091s, Hepatic C Viral Kinetics in Subjects Co-infected with Human Immunodeficiency Virus-1 (HIV-1) and Hepatitis C Virus Genotype 1 (HCV-1); [AS PER AMENDMENT 07/20/01: The following text has been deleted: or A5092s, Evaluation of the Effects of Ribavirin on Zidovudine (ZDV) or Stavudine (d4T) Triphosphate Formation] [AS PER AMENDMENT 07/20/01: Substudy A5092s, Evaluation of the Effects of Ribavirin on Zidovudine (ZDV) or Stavudine (d4T) Triphosphate Formation is now a stand-alone study.]