After completing the upgrade to vCenter Server, upgrade legacy VMware ESX/ESXi hosts to ESX 4.0/ESXi 4.0.

These topics are intended for administrators who are upgrading ESX, ESXi, and virtual machines from ESX 3.x/ESXi 3.5 hosts to ESX 4.0/ESXi 4.0. One topic discusses the upgrade path from ESX 2.5.5.