Before you upgrade an ESX/ESXi host (Choose Three):

Before you upgrade an ESX/ESXi host (Choose Three):

A.
verify current hardware is supported per the vSphere Systems Compatibility Guide

B.
run the VMware CPU Identification Utility

C.
run the vSphere 4 Pre-Upgrade Script from the command line

D.
schedule a maintenance window for 32-bit hardware

E.
compare the md5sum of the downloaded file to the value on the VMware download website

Explanation:
Ensure that the hardware and/or virtual machine meets the minimum system requirements for VMware vCenter 4.0

You can use vSphere Host Update Utility to upgrade ESX 3.x to ESX 4.0 and ESXi 3.5 hosts to ESXi 4.0. You cannot use vSphere Host Update Utility to convert ESX hosts to ESXi hosts, or the reverse. When you select a host to be upgraded, the tool performs an automated host compatibility check as a preupgrade step. The check verifies that each host is compatible with ESX 4.0/ESXi 4.0, including the required CPU, and has adequate boot and root partition space. In addition to the automated preupgrade script, you can specify a postupgrade configuration script to ease deployment. Note the preupgrade script is automated and so does not need to be run explicitly. ESX and vCenter Server Installation Guide, ESX 4.0 vCenter Server 4.0, page 13.
ESX Hardware Requirements
* 64-Bit Processor