Shadowrun and Halo 2 - the first champions of Windows Vista gaming - have already been cracked by 'warez' and hacking groups, with patches enabling both to function on Windows XP available.
Both games have been released as Vista exclusives in recent weeks, introducing an Xbox Live-style service to PC gamers.
The news that the games will run on XP won't come as much of a surprise to close observers after Falling Leaf Systems boldly claimed in May that it planned to offer compatibility software for both games "within a few months".
At the time, CEO Brian Thomason wrote: "First [Microsoft] claim that it was impossible to implement DirectX 10 compatibility atop Windows XP, and now they also want us to believe that they couldnât successfully launch two DirectX 9 based titles on XP either. We plan to expose both theories as patently false."