Reset Network settings to default

It did not work. I tried deleting com.apple.NetworkUtility.plist and I am still connecting to the internet. Then I tried com.apple.airportutility.plist (I could not find the one that you said airport.preferences) and then I tried com.apple.preference.internet.xxxxxxxxxx.plist. None of this worked. I am still connected to the internet with my old configuration. Any ideas as to what I am doing wrong?

The reason I want to reset it is because I think I accidentally deleted the automatic option in the locations area. What I would like to do is just go into edit locations and choose automatic but that option is not there. I just have one location in the edit locations box and I can't delete one location. At least it does not give me the option to delete the one location. Would resetting it bring back the Automatic option or because I deleted that does that mean I can't get that back?

I am not going to try and reset my settings anymore. It seems to be working ok. My question is I deleted that NetworkUtility.plst file. Is that ok or will the system need that file?