The new operating system -- it debuted to consumers Tuesday -- is incompatible with scores of so-called "casual games" available for download, including some on Microsoft's own MSN portal, said Alex St. John, the chief executive of game network WildTangent, and formerly a Microsoft developer who was one of the creators of the DirectX graphics technology.
"Microsoft has gone overboard in making Vista so secure that the restrictions have broken most online games," said St. John in a statement.
Casual games are those typically produced by independent game developers, and target a non-gamer audience.
St. John also blasted Vista's parental control feature, which lets adults limit the content children can use or view on a PC. According to St. John, Vista relies heavily on Electronic Software Ratings Board ratings to block access.
"Parents who choose to use Vista's parental controls are likely to accidentally block access to hundreds of very popular family friendly games that happen not to have ESRB ratings," he said.
WildTangent has posted a free-of-charge game console to its Web site that it claims lets Vista users 300 different downloadable games.