Scenario 1: Moving a VM from Workstation to ESXi - MAC/uuid change
The solution is modify the .vmx file for the VM on the ESXi server. I'd recommend copying the vmx file to an alternate name (i.e., cp myVM.vmx myVM.vmx.backup.) Do these changes at your own risk:
1. Shut down the VM
2. SSH to the ESXi server and find the vmx file in question (somewhere in /vmfs/volumes/name/of/vms/directory
3. Edit the file and replace the following 4 (or more lines) with the equivalent values from the Workstation vmx file:
uuid.location = "56 2d af 08 59 0b 10 8c-78 9d 96 3d 9c 82 fe d4"
uuid.bios = "56 2d 92 33 47 3b 9e 16-e1 12 56 db 8f 32 4f 3f"
vc.uuid = "52 c3 f7 68 14 da 8f a4-16 a1 d1 54 07 85 f3 16"
ethernet0.generatedAddress = "00:0c:31:33:4a:3f"
You may have more than one ethernet interface, so change them all.
4. Remove the VM from the ESXi server's inventory (but do not remove it from Disk!), so that it will notice the change (this is done in configuration -> storage management, of course.)
5. Add it back to the machine's inventory
6. When you start it up now, it should have the same ethernet MAC addresses.
Scenario 2: Moving a VM by removing it from the inventory of one ESXi host to another ESXi host
In this case, the VM was shut down. It resided on shared storage, so the other hypervisor head could see it. When importing it into the new machine, the person performing the operation chose "I copied it" instead of "I moved it."
This was more complex. The solution is very, very similar.
1. ssh to the new ESXi host
2. cd to the VM's directory
3. look for old log files and cat out the info you need (for instance, if the "copy" happened today, a log file from yesterday would suffice (ls -la vmware*.log)
4. Assuming the older log file is called vmware-1.log,
cat vmware-1.log | egrep egrep "(generatedA|uuid)" > mydata.txt
5. make a backup copy of the vmx file
6. look in the mydata.txt file and grab the data you need.
7. edit the vmx file and replace the appropriate lines from the current config with the config from the mydata.txt file. You'll need to remove some text from mydata.txt
8. remove the host from ESXi's inventory and re-add it.