ZHPCleaner is a free portable tool which can detect and remove adware, browser hijackers, some toolbars and more.
The program is very convenient to use. There's no installation, it doesn't even arrive in a ZIP file, you just download, run and hit "Scan".
You might see occasional dialogs and prompts during the scan, and these aren't always straightforward. "Have you installed this server?", the program asked, displaying a couple of IP addresses we didn't recognise. What server? ZHPCleaner didn't explain, so we clicked "No" and waited to see what would happen.
Once the scan completes, the program becomes more straightforward. There are lists of "problem" settings and possible adware traces, all checked by default, but you're free to browse and clear anything you'd like to keep. (Our "Server" turned out to be the DNS servers of an uninstalled VPN service, so we allowed them to be deleted.)
Hit the "Repair" button when you're ready and ZHPCleaner cleans any selected settings or traces, prompting you to reboot to ensure any active adware is removed.