To register an existing virtual machine to your vCenter inventory, you have to specify the path to a .vmx file. A .vmx file contains the configuration for an existing virtual machine. Here are a few lines from a .vmx file:

.encoding = "UTF-8"
config.version = "8"
virtualHW.version = "10"
vmci0.present = "TRUE"
displayName = "vm4"
extendedConfigFile = "vm4.vmxf"
floppy0.present = "FALSE"
memSize = "256"

You typically don't modify a .vmx file with an editor, because you might break the connection to the virtual machine. The VMware Knowledge Base article (available at http://kb.vmware.com/kb/1714) gives tips for editing a .vmx file.

The following example will register a virtual machine named VM4:

PowerCLI C:\> $Cluster = Get-Cluster –Name Cluster01
PowerCLI C:\> New-VM –Name VM4 –ResourcePool $Cluster `
>> -VMFilePath "[Datastore2] VM4/VM4.vmx"
>>

The output of the preceding command is as follows:

Name                 PowerState Num CPUs MemoryGB...