I have a 3550 Catalyst switch once I power it up, It displays this error message "!!! Warning: This switch is not usable !!!". When I did show run, both the Gigabitethernet/fastethernet ports did not display. If I plug my laptop to the switch my LAN connection shows connected but no light displays on the switch. I assumed the switch has hardware error, or can somebody figure out what the problem is. I have change the IOS several time but still the same problem.