There didn't seem to be a dedicated Virtualization SE, so...
I am looking to install VMware vSphere Hypervisor 5.1 (or an older version if it helps) on a 64bit AMD A8 architecture.
Is there a path to doing this without destroying/having to reinstall Windows 8 already preinstalled by the Vendor (Acer), making it one of the VMs instead?
Or in general? (Eg. on another PC running 32bit Ubuntu, where I would like to "insert" a Hypervisor as well).
Use VMware Converter. It converts a physical machine into a VM during runtime. It is freely downloadable after registering on the VMware site:
http://www.vmware.com/products/converter/