On most routers, port forwarding must be explicitly turned on
for a specific port/IP combo. So, if you haven't turned it on, then you needn't turn it off. That being said, you may want to check to ensure that nothing has been turned on by someone else. You can do this from the router's control panel which is usually accessible by entering its IP address in you browser's address bar. The default IP address depends on the make and model of the router (you can look it up on Google) and usually looks something like 192.168.x.x where x= a number from 0 to 255. The precise steps to follow in the control panel also vary widely from model to model.
Edited by Andrew, 19 September 2010 - 05:50 PM.