It's likely in his connection settings. I can't remember where in Win7 or Win8.1 thes are stored, but essentially, there's a tick box that says "use this proxy for all connections". Sometimes those add-on toolbars will add a proxy that points to their servers so they can serve you crazy ads.
Ah, here it is. On my win7 machine, if I go to the run box and type "proxy", in the search results you'll see "Configure proxy server". Click that link, and it should take you to the Internet Properties dialog. Click on Lan Settings at the bottom, and you'll see a dialog that talks about the Proxy server. delete the info in the Address box, and uncheck the "Use a proxy server..." then hit OK. It should delete the proxy server, and start to send all it's traffic through whatever gateway your ISP uses.