To celebrate the launch, Microsoft is running a week of daily deals on select games. Today's offer is a 50% discount on Borderlands, bringing it down to $9.99.

The launch is also celebrated with news that titles from publisher Activision have been added to the catalogue. While Activision's lineup includes Call of Duty 4: Modern Warfare and CoD: World at War, the series' latest two entries are notably absent.

"If a game is a Steamworks game, it's not something we're selling," Microsoft's product manager for PC and mobile gaming, Peter Orullian, has told us. This'll preclude CoD: Modern Warfare 2 and Black Ops from being sold in Microsoft's store, not to mention an ever-increasing number of other high-profile PC games. However, similar claims were once made by fellow digital distributor Direct2Drive, which soon changed its mind.

As well as debit and credit cards, the GFWM store accepts Microsoft Points as payment.