|What's the make and model of your router?|
I've never encountered a lock symbol on a router before but in normal circumstances pressing and holding (10 seconds) the reset button on a router would reset it back to factory / default settings.
Resetting the router would mean setting up all of your security again.
Are you able to access the routers configuration page from the desktop? I'm assuming it is connected to the router via cable as opposed to connecting wirelessly.
Give us the make and model of the router and we will look up the default login details for it. The guy who set up your router should have left you the login details if he changed them. Chances are he didn't and it could simply be a matter of entering admin username and hitting enter leaving the password field blank or entering "password" for the password.
message edited by btk1w1