Some time ago I defined a Windows Server 2003 VM in Vsphere 4.1 and chose the default options. One of those probably was using a 32 bit vCPU. I wanted to upgrade that VM to Windows Server 2008 but the upgrade blue screened on me. Not sure, but I suspect it is looking for the 64 bit instruction set and can't see it.
Is there a way to determine if this VM is defined as 32 bit only, and if so, is there a way to 'upgrade' the cpu to 64 bit?