Clean Up Computer

So. The cable guy came over to fix our internet connection, because it wasn’t working since we came back from vacation. He went on my laptop in the living room and the pointer went haywire (I don’t have a mouse, it’s just a touch pad). He said, "Looks like you have a trojan" and I was like whatever. That was the first time it happened.. but now it’s happening more often. And now I can’t connect to the internet, even when I’m right next to the signal thingy.Sorry if I’m vague and non-descriptive but I don’t know much about routers and stuff.. so here goes.
There are 3 computers in the house. 2 have wireless connection and 1 is wired. We don’t have dial-up, and we the company that gives us our internet is the same as the one that gives us cable and phone connection. My mom’s computer works fine in my room but my laptop doesn’t (they’re both wireless). The black rectangular prism shaped box by my sister’s computer with the blinking lights that say cable, send, receive and power (among others) is brand Scientific Atlanta and is model DPR2320R2. It also says cable modem/gateway. The signal thingy that is connected to it is D-Link. Also, the internet connection detection thing in the bar in the bottom right corner on my laptop says that my wireless internet connection is excellent, but even then I can’t view any pages in Firefox. I ran a virus scan but all I found was something with Win32 in it, and the virus program couldn’t remove it.. Right now I’m running trend micro house call (online virus scanner). If it helps, I defragged my computer this morning after running Eusing’s free registry cleaner (380 problems detected). I’m really sorry if this isn’t enough information, just ask if you need any more. Thank you 🙂