A TechHead reader recently experienced the following message in VMware vSphere (ESXi) when trying to start a 64-bit VM (Windows 2008 R2) running on their HP Proliant ML110 G5: “This virtual machine is configured for 64-bit guest operating systems”, “However, 64-bit operation is not possible.”, “Longmode is disabled for this virtual machine.”.  This is an error that can often crop up especially when dealing with nested VMs or when deploying new ESXi hosts. The typical reason for this message is … [Read more...]