Peter was looking for video codecs and he got bit by some malware called "Search Donkey." Leo says that even legitimate sites can get bit by malware. And places like CNet will install adware in their installer without really drawing attention to it. Leo says that the only difference between Malware and Adware is that Adware lets the user uninstall and technically gives an opt out on installation (if the user can find it). But the problem with Codecs are that they are owned by someone and if he doesn't get them from the official site, chances are, it's either pirated or connected to malware.
Search Donkey is likely a browser hijacker. Peter should try uninstalling it from add/remove programs. If it's still there, then it's malware. Leo recommends going to MalwareBytes.org and run that. But only get it from MalwareBytes. There's a ton of copycats that will install malware. Also check out tips and tools at BleepingComputer.com, including a cleaning tool that will take it off.