Why wont my laptop connect to internet? PLZ HELP?

My sister's laptop used to work fine. But then my mom couldnt connect to nternet on the desktop so she unplugged and replugged some things. still didnt work. My sisters internet was working either, but i dont kno what didnt work first. I reseted internet explorer an it worked on the desktop. Not on laptop. It does the internet explorer cannot open webpage thing, and google chrome says that its unavailable. i checked the network connection thing, and it 'looked' fine. I tried the cmd-ipconfig-netsh-msconfig stuff. ALL OF THEM! nothin works. I dont kno if its the modem or wirless router or laptop. PLEASE HLP! if u need more info just say so.