To completely reset to defaults, use a paperclip to push the "managed mode" button.  Hold the button for 30 seconds.  wait about 3 minutes for the switch to reset and come up in unmanaged mode.  push and hold the managed mode button again for 30 seconds.  wait about 3 minutes for the switch to come up in managed mode.  Now try again. Default IP address is 192.168.2.1.   Try pinging this address before accessing via web.   Make sure PC is directly connected and on 192.168.2.x network. Another thing to note is the duplex of your connection.  I have seen management issues on this switch if there is a half duplex connection to the management pc.   A half duplex connection can result from the management pc not having autonegotiation set.
I have a PowerConnect 2708 that I would like to reset back to factory settings.  It shows it is in managed mode, but I can't get to the web interface. I'm not sure what the current IP of the switch is. I I connect a laptop to it that is set to DHCP, and I do an ipconfig, I come back with an IP Address on the laptop of 169.254.8.x, and a subnet mask of 255.255.0.0, but it doesn't show a gateway.  I tried to take it out of managed mode, then put it back in, but that didn't seem to work. What should I try next?   Thanks, Rob
PowerConnect 2708 Reset