I posted this for another person with the same problem in another thread ,but I'll post it here again for you. What you should do is check on your router settings [often 192.168.1.1 or 192.168.0.1 is the address to access them] username leave blank and password should be admin or password, then make sure all the settings are correct. Also check on your nic card properties, going to Control Panel, Network Connections, right click on the card that you're using, then Properties, then look at the options you have, under "this connection uses the following items:" look for "Internet Protocol [TCP/IP]", select it, then click on the Properties button and make sure the 'obtain ip automatically' is checked, same for DNS... if that doesn't work, then leave that where it is, go to your your computer [which is the one that works], go to Start, Run, type cmd, type " ipconfig /all " ... write down all the numbers corresponding for IP address, Subnet Mask, Default Gateway and DNS numbers, both of them. Then go back to your dad's computer to the same place I told you before, type in all those numbers, but you will need to change the IP number, your ip should look like this: 192.168.1.100, the last number could be different, it could be 9 or whatever, change that number on your dad's computer to a number a bit higher than the ip on your computer, if yours is 100 then change it to 101 or 102 blah blah, then apply the changes. Restart computer if necessary [though it shouldn't be] and try going online again. 
AJ