You need to access the router configuration and change the channel setting, and also set wireless security.
You need to get the IP address of the router, click start, run then type "cmd" without the quotes and press enter.
At the prompt, type "ipconfig /all" again without the prompts, and press enter, identify the IP address entry for the default gateway and write it down.
Open internet explorer and put the above IP address after the
http:// and press enter, you might now be prompted for a username/password, this depends on the make of the router but try admin/admin or admin/password
You then need to find the sections relating to channel and wireless security.