Win32ole with 'VirtualServer.Application'?

require 'win32ole'
vs=WIN32OLE.new('VirtualServer.Application')
vm = vs.FindVirtualMachine("Windows 2000 Server")

the error:
WIN32OLERuntimeError: FindVirtualMachine
    OLE error code:80070542 in <Unknown>
      <No Description>
    HRESULT error code:0x80020009
      Exception occurred.
        from (irb):22:in `method_missing'
        from (irb):22

what is wrong?

Thank