Back up your data.
Check through Windows Add/Remove programs for anything that shouldn't be there and get rid.
Go the Settings page of Chrome. In the Advanced section there should be a "restore to default" option. Can't remember exactly where. And they've probably moved it. Do that - it will reset Chrome back to fresh state.
Run ADWCleaner or an anti-malware program of your choice and clean it up.
Those kind of things are known as "browser hijackers" - a quick Bing for how to remove them will give some more detailed results.
Go Google Free. They are insane now with shoving ads at you.
I cut out everything Google recently and could not be happier. It's the only way they will learn is if people stop running to their products and begin running away.