The study hypothesis is that in stable, virologically suppressed (plasma HIV-RNA <200 copies/mL) patients with no history of prior virological failure, a switch to either MVC dosed at 300mg twice daily (bid) combined with the same 2N(t)RTI backbone regimen or MVC dosed at 150mg twice daily (bid) with the current PI/r (or 300mg bid at the discretion of the investigator if the PI/r is fosamprenavir/r) provides similar (non-inferior) antiretroviral efficacy compared to continuation of the current 2N(t)RTI + PI/r regimen.