Not sure how you "set the router off the default channel". So, open your browser and enter the address of your router, i.e.,
http://192.168.1.1 - you will then be asked for a username/password, the default is admin/admin unless you changed it, of course.
That will take you to your router setup screen. You didn't give a lot of info about your setup but you can change the channel there. Just go to the Wireless tab - while there you can also limit to "b" only or "g" only, depending on your computer's ethernet adapter if you want to try and further limit access. Since default is channel 6 choose 1 or 11 - if that's not working try 3 or 9 for example. Just try to get away from something others would choose.
The Network Stumbler I mentioned is a program you have to download from the web. If you can't do downloads, then don't worry about it - it takes some networking knowledge. If you do try to download it, it can tell you as you walk around the room whether you have a strong or weak signal from your router. If you feel this is too advanced, not to worry...and don't worry about the AP and such...we'll talk about it later if you need it.
Try setting the channel first. If I'm not being simple enough tell me and I'll go step by step until we get it setup correctly. zeroth