Downgrade a VMware VM from version 10 to 9 the easy way,

Using the vsphere client power off the VM.
The in the summary tab, right-click on the Storage icon and choose Browse Datastore.
Browse to the folder that contains the VM name you wish to down grade: in this case TEST-VM
Now copy the TEST-VM.vmx to another location as a backup. Right-click the file and choose copy.
In another folder or the root paste the file, in case you need to revert back to the original.
Now put the mouse over the platter disk icons in the Datastore Browser. It will pop up what each one does.
We want to use the one that allows you to download from the datastore to the local PC and download the TEST-VM.vmx file to the local PC.
Edit the file with notepad, you will need to right-click and choose Open with and choose notepad.
In the first line you will see:
virtualHW.version = "10" Change that to be virtualHW.version = "9" now save the file.
Back to the Datastore Browser and now we need to delete the file TEST-VM.wmx from the folder.
Now put the mouse over the platter disk icons in the Datastore Browser. It will pop up what each one does.
We want to use the one that allows you to upload files to the datastore. Now upload the file to the folder you just deleted it from on the datastore
Power on the VM and it will now be version 9 and you can now edit it with the vsphere client.

Or you can enable SSH on the Vhost
Use WinSCP.exe and do this all via a GUI interface.

All you need to know is were the VM is stored (aka which datastore) the userid and pwd into the vhost.
Login with WinSCP browse to VMFS/Volumes/VMName
Find the VMName.vmx file, right-click it and choose edit and then
In the first line you will see:
virtualHW.version = "10" Change that to be virtualHW.version = "9" now save the file.
It will now be version 9 and you can now edit it with the vsphere client.
the Power on the VM.