Chris Donahue, manager of Microsoft's Games for Windows group, says the company has tested 1,000 popular games from the past five years. Most work well with Vista, he said, declining to elaborate how many had problems and why.

Vista's DirectX 10 is a complete rewrite of Microsoft's graphic engine that should allow games written for the platform to run much faster and display more textured, lifelike images than under DirectX 9.

DirectX 10 is so advanced that even Vista's advanced desktop interface, dubbed "Aero," relies on the previous-generation DirectX 9 technology.

Leading game publishers such as Electronic Arts Inc., PopCap Games Inc., Vivendi Games, THQ Inc., Slam Games and WildTangent Inc. are busily creating games taking advantage of DirectX 10, according to Microsoft. Microsoft, through its MSN Games group, is also releasing a number of less graphically-intensive "casual" games for Vista.

But so far, Microsoft has only shown off -- and only via screenshots and video clips -- a handful of games that truly take advantage of DirectX 10. And many of those improvements appear to be subtle ones that only the most avid gamers will notice.