Confirm that the virtual machine is actually unresponsive. It is possible that the virtual machine is not responding via one interface, but is functioning correctly on others. For more information on testing whether a virtual machine is genuinely unresponsive, see Confirming whether virtual machine is unresponsive (1007802).
If a virtual machine is responsive, but performing poorly, see Troubleshooting ESX virtual machine performance issues (2001003).
Verify that the virtual machine is powered on. If the virtual machine has been powered off unexpectedly, power it back on and then troubleshoot the cause of the unexpected shutdown. For more information, see: