Solving computer wifi problems?

Okay, since late last night I've been unable to connect to my home internet using my laptop's internal wifi adapter. I memorised the passcode so I know it's right, but when I input the code to try and connect it says "the network key is incorrect. Please try again." I know that it's right because it was working yesterday. I have the free few however many days (summet like 60 days) of Norton Internet Security that came with my laptop running and have done since I got the laptop. I've downloaded multiple mods for minecraft, I downloaded two or three last night also. Next to that I found that there was a flash virus trying to get through, norton told me, and kept closing webpages I was trying to look at. So I uninstalled flash and reinstalled it but when I went to youtube I couldn't watch any videos because of flash. So I restarted my laptop to try and get it to work and on restart the internet wasn't working (the aformentioned problem) so I did multiple restarts to try and fix it to no avail. So i did a system restore to the last restore point that worked. But still no internet. I've plugged in the stupid wifi adaptor to use the internet for now, and youtube works and everything works fine except the internet. Someone help

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