In just a week, on August 22, the Xbox.com PC Marketplace is to close, though previously purchased games will still be available to download.
The full statement can be found here, but the most significant part reads:
As part of the recent Xbox 360 system update, Microsoft Points will be retired and the Xbox.com PC Marketplace will be closed as of August 22, 2013. We encourage you to spend your Microsoft Points balance prior to this change. Although you will not be able to purchase new games, you can continue to enjoy previously purchased content by downloading it through the Games for Windows Live client software as usual.
All in all this likely won’t have a huge effect on many people, with the Games for Windows Marketplace service being probably the most maligned of all the PC digital game distribution services.