This video will show you how to install ESXi 5.0 on a drive with an existing ESX 4.1 installation and VMFS datastore present. ESXi 5.0 uses the same installer for fresh installations and upgrades. If the installer finds an existing ESX 4.x or ESXi 4.x installation, it allows you to performs an upgrade.
During this upgrade, the ESXi installer will offer several options for preserving or discarding existing ESX host settings and VMFS datastores. If an earlier version of ESX and VMFS was found by the installer, it will show you the selected storage device contains an installation of ESX and a VMFS datastore. You can choose whether to upgrade or install and overwrite the existing installation. You can also choose whether to preserve or overwrite the existing VMFS datastore. After upgrading from ESX 4.1 to ESXi 5.0, only the relevant settings will be migrated.