Explanation/Reference:
Explanation: Before you upgrade the virtual hardware:
1. Create a backup or snapshot of the virtual machine. For more information, see:
Take a Snapshot in the vSphere Web Client section in the vSphere 5.1 Virtual Machine Administration

guide.
Take a Snapshot in the vSphere Client section in the vSphere 5.1 Virtual Machine Administration guide.

2. Upgrade VMware Tools. On Microsoft Windows virtual machines, if you upgrade the virtual hardware before you upgrade VMware Tools, the virtual machine might lose its network settings.
3. Verify that all .vmdk files are available to the ESXi/ESX hosts on a VMFS 3, VMFS 5, or NFS datastore.
4. Verify that the virtual machines are stored on VMFS 3, VMFS 5 or NFS datastores.
5. Determine the version of the virtual hardware by selecting the virtual machine from the vSphere Client or vSphere Web Client and clicking the Summary tab. The VM Version label in the Compatibility field displays the virtual hardware version Reference: https://kb.vmware.com/selfservice/microsites/search.do?
language=en_US&cmd=displayKC&externalId=1010675