Hacked

My computer was hacked many year's ago Back in 2004 I think, When this happened I used to get a message all the time saying "other people were logged into this computer" when I was the only person who used the computer I lost the ability to host games on Xbox 360. I found all the stuff installed on my computer on my Norton antivirus Things that slowed my internet connection down and made me lag in games I know how this was done to me My original Xbox was hacked and whoever done it must of got my information from my Xbox live account and then somehow got into my computer Anyways ever since then my internet connection is slow I have changed ISP numerous times and it still remains the same. I never knew how to fix this problem and have never tried to fix it as I refuse to pay money to a technician to fix the problem all in the hope I have some sort of evidence and proof that someone hacked into my computer and Xbox. I recently changed ISP again from a 150gb Eir connection to a 500gb Virgin media The speeds are ridiculous sometimes it's under 1 mb the most it goes to is in the 20's Problem is now I can't even get on the internet with the router/modem from virgin media When I try to set a wireless network on my Xbox one it says DNS isn't resolving Xbox server names. When I try entering my network security key on my laptop it says that it is wrong even though I entered the password correctly. All I can do for the moment is use the internet from my phone by creating a hotspot There's obviously something really wrong with the broadband line/cable in my home. I rang Virgin media customer support and they have arranged for a technician to come out to my house to have a look at it. Can a broadband line/cable be hacked itself? Can anyone please help me out with this problem? I still have the old computer and original Xbox that were hacked This has gone on far to long I need to sort it out