Malware removal

If there are any toolbars or search addons listed in Programs and Features, try to uninstall them from there first. Sometimes that's enough to get rid of it.

Check your list of browser extensions and add-ons, remove anything suspicious, sometimes adware will install as a "managed" extension and chrome won't let you remove it, you'll have to delete the whole chrome folder in AppData and then reinstall.

Also run MSConfig and disable suspicious startup items that aren't supposed to be there. (Google the name if you're suspicious.)

If neither of those fix your problems, try scanning with Malwarebytes Anti-Malware, then if that doesn't fix it, try TDSSKiller and F.Secure Blacklight.