Games for Windows Software Setup 3.5 has been released and it is now available for download from the Microsoft Download Center. Games for Windows Marketplace Software Setup 3.5 is the next avatar of the old Games for Windows Live.
Games for Windows
Games for Windows Marketplace delivers great games at great prices and gives you access to Games for Windows - LIVE, a free online gaming service that lets you connect and play with your friends and millions of Xbox LIVE members.
The Software Setup 3.5 upgrades users to the newest version.
Download page : Microsoft.
Update: Although you may not be able to purchase new games, you can continue to enjoy previously purchased content by downloading them through the Games for Windows client software as usual.