A blank file "shouldn't" hurt anything. Basically modprobe.conf is used to assign modules to devices. For instance for your first wireless device it would normally be wlan0, if you are using ndiswrapper for the driver ( module ), you should have:
alias wlan0 ndiswrapper
in your modprobe.conf. So when it goes to activate your wireless it will see that entry and load ndiswrapper. If all of you hardware is still functioning correctly right now, I would say that you are fine. Possibly you just didn't get it saved right. You didn't use vi did you? I like nano as a cli text editor as opposed to vi. If you are in gui than use gedit.