Computer networks yellow triangle exclamation point, not even the Internet ah ah?!

With their own dormitory broadband, mobile phones also attached properly, the computer will die one day, several days, opened a hot spot what Rom, no matter what network show even without a network, check the internet say ip address is the problem? but what followed tried to change the address of no use. Tried many methods will not work. . If experienced people can save me about it. . .