Yes. Your contact doesn't need to have a USB phone. All they need is a PC headset, or a microphone/speaker setup, or an actual phone through which they can accept your incoming Yahoo! Messenger call.
Note: A conversation between two USB phones will provide the best user experience. Neither of you need to be sitting at the PC to place or take the call!
Where's the Contact Customer Care button? With so many improvements to Messenger since the version you're using (lots more features and reliability), we figured you're ready to move up. So get your upgrade and with the new version, rest assured if you have questions, you’ll find that friendly button on its help pages.