It had been claimed that neither title would be able to run successfully using the older DirectX 9 graphics engine, with Microsoft urging gamers to take the plunge and switch to the Vista.

The news is sure to irk Microsoft who may now face an increased delay in some consumers adopting Vista at this early stage. However, it shouldn’t come as a surprise. Earlier this month Falling Leaf Systems  said in a press release that it believed Microsoft was deceiving consumers by stating that the titles would only work on Vista, and announced its intentions to release compatability software to disprove the claim.

“Microsoft has, in typical Microsoft fashion, decided to launch their forced migration onslaught in full force with the release of two games that will only run on Windows Vista,” said Falling Leaf Systems CEO Brian Thomason in the press release. “First they claim that it was impossible to implement DirectX 10 compatibility atop Windows XP, and now they also want us to believe that they couldn’t successfully launch two DirectX 9 based titles on XP either. We plan to expose both theories as patently false.”

It appears Warez has beaten Falling Leaf to its goal, although Windows Live and in-game achievements are features still only availalbe to Vista gamers.