After changing the Dell 790 PSU No router [Closed]

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Hello,

I have a Dell 790 Win 7 and the power supply went bacd. Replaced with a Dell OEM.

Everything is connected properly. Problem, router is not recongnized...no internet even if I plug it in directly to the modem. Tried a nymber of fixes no luck. Tried sys restore problem with 0X80042308. Additionally when booting up a square window appears but could not read the message. Any thoughts. FYI my experise is in real estate valuation not so much with computers!