Welcome to Seven Forums,
Start off with Power cycle:
Turn off your computer and unplug the modem. Turning your modem off may not be enough to get it to restart itself, so always unplug its power source. Leave your modem off for 1 minute, then plug it back in and turn on your computer.
Do an ipconfig /all from your computer, compare the output of yours and your cousin's.
Click on Start => in search box type cmd press enter. From the black screen, type the word ipconfig /all and press enter. Right click on the black screen or Command prompt then choose Select All and Paste the results onto your Post.
You may also try these commands from your computer. Click on Start, type cmd, from the command prompt type:
ipconfig /release then press enter
ipconfig /renew then press enter