Wondering why you couldn't find a Windows version of Halo 2 in stores on Tuesday? Well, the answer is finally out - Microsoft has delayed the game's May release for a second time.

Earlier this month, we reported that Halo 2 for Windows Vista was summarily delayed from its original release on May 8th to a later date on May 22nd. Well, May 22nd rolled around, Halo 2 didn't appear in stores, and hardly anybody noticed or made a fuss. Until now, of course.

On Thursday, Microsoft made another announcement regarding the release of Halo 2 Vista, which has been delayed for another week or so. The new date for North America is May 31st, while the date for the European release has been set to June 8th.

According to a recent post on Joystiq, a Microsoft representative told the blog today that Shadowrun has now been given the title of the first game to debut for the Games for Windows -- Live service. The FASA-developed FPS will be released to both Vista gamers and Xbox 360 owners on May 29th.