If you use an existing virtual machine and upgrade the virtual hardware, you gain access to new features, but the process is one-way — you cannot reverse it.

Start by using an existing configuration file (.vmx) and virtual disk (.vmdk or .dsk).

Upgrade VMware Tools to the new version, following the instructions in Installing VMware Tools. Do not remove the older version of VMware Tools before installing the new version.

Upgrade the virtual hardware so you can take advantage of better performance, improved networking, support for taking a snapshot while the virtual machine is running and improved virtual disk formats. See Upgrading Virtual Hardware in the Guest Operating System.