Have you looked at the Nortel network site

for any discovery or management software? The only reason you'd need to get into the web interface is for management purposes. Of course you'd need the IP address. If you know or can discover that, you might be able to use a web browser and just http://(IP address) to get to the interface. Your next dilemma will probably be the admin password. If that's been set, you may be dead in the water. Whether or not you can just use the switch as is depends on what someone may have done with the individual ports. They could have been disabled, locked to a MAC address, limited in connection speed, or any of a number of things an administrator might to to control traffic. Have you tried just connecting a few devices to it to see if they connect to your network? If it won't work as a stand alone switch, I'd think it's either defective or it's been altered by someone.