Study to investigate the effects of steady-state TPV/r (500 mg/100 mg BID) on the single-dose and steady-state pharmacokinetics of Atazanavir (300 mg QD) co-administered with Ritonavir (100 mg). To investigate the effects of single-dose and steady-state Atazanavir (300 mg) on the steady-state pharmacokinetics of Tipranavir and Ritonavir.