Help..Internet is connected/dosent work

I am new here, and i need help bad. I do not know alot about computers so if you are going to help me i will need detailed instructions on how to do things. First off I live at home with my parrents and my brother. We all have our own computers and each compter is connected directly to the internet, but we also have a Lan cannection that allows us to transport files to each computer. My brother is a genuis with computers and he knows how to do alot of things. Over the summer we got in a fight about a game (World of Warcraft) and the day after the fight im am playing WoW and all of a sudden i get dissconneced. shortly after my internet isent working, i know it was my brother because he has done this before but i never knew how to fix it. Layter that day he goes to his friends house mean wile i am stil trying to figger out what he did. I find out that his computer is on and has a program running, He is logged out so i cant see what the program is but i still shut down his computer any ways. When i go in to my room the internet works! I now know that when my internet isent connected to look if his computer is on. Frst off i would like to know if there is a program that does this. I resently have got in a fight with him agen and its about the same game(maby i should stop playing games)this time the same thing happands but he denies doing anything. When i go back to check my internet connection it is connected but i cant go on msn, firefox, IE, or use any of my internet privlages. I keep on looking to see if i can resulve the problem. Shortly after he turns off his computer but i still cannot do anything. I try to see it my parrents computer has the same deal. It works fine So i switch my Tower with thir tower Still dosent work for me. I gess this means that the problem is only with my computer. Layter i asked what he did he plays dumb dosent know what im talking about and suggested i have a trojan or somthing. I said that i dident download anything and all i was doing was playing World of Warcraft he said that its possible. I think he was just trying to fool me. But anyway im pretty sure that the problem is with my computer. Sorry about all my spelling and grammer. Please help.

Things i need to know
- Is there a program that disables another computers internet
- Can u get a trojan from playing online game and talking on msn
- How to fix my Computer so that So that my internet works.
Any suggestion will be fine

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