Google talk was discontinued on February 23rd 2015. It is recommended giving Hangouts a try so you can chat with all your Google contacts. Hangouts supports people’s favorite features from Google Talk, including text chat, presence, contact lists and status messages. In addition, Hangouts lets you have group video chats, make phone calls, express yourself with emojis and keep your conversations going across Android, iOS, and your computer.
If messaging right from your desktop is important to you, try the Hangouts Chrome app or Hangouts in Gmail. If you’re not ready to make the switch to Hangouts quite yet, you can continue using Google Talk on Windows with a range of compatible third-party chat apps. (Please keep in mind these aren’t Google products, so exercise caution when signing in with your Google account.)