There is no way to reset the switch unless you can somehow get to the management interface of the switch.  Normally serial interface should be available to you even if everything else is not available at this point.  However if you can't even get to serial then there is really no way to reset the switch.  Make sure you check your serial settings and use different computers to try to connect to the switch.  I have had a computer serial interface locked up before.

Anyway, if you still can't connect to your management interface somehow then I suggest you call Dell technical support for further help.

Cuong.