Microsoft on Wednesday said its Live online service, which has attracted 6 million Xbox 360 console gamers, will be open in May to PC gamers who use its new Windows Vista operating system. The move comes nearly a year after Microsoft Chairman Bill Gates said the company's vision was for "anywhere" gaming that would link video game consoles, cell phones and computers, and is a key step toward reaching that goal.

The PC version of Live will debut on May 8 with the launch of the Windows Vista version of "Halo 2," Microsoft's popular alien shooter game.

In June, Microsoft Game Studios will release "Shadowrun," the first game where Live will support competition between players on the Xbox 360 and PCs.

Live members will need just one account, whether they play on the Xbox 360, the PC, or both machines.

Microsoft offers two Live subscription levels. Silver membership is free and the Gold level, which includes cross-platform play costs about $50 per year. Gold level also gives users the additional option to unlock multiplayer achievements, search for gamers of an equivalent skill level and compete on either platform in supported games. Both memberships include a multiplayer game browser so users can track down servers supported by Games for Windows Live titles.

The service will only be available to PC owners using the new Vista operating system.

Microsoft's online gaming service has been a key selling point for its Xbox 360 video game console, which was released in November 2005 and competes with Sony Corp.'s PlayStation 3 and Nintendo 's Wii for top billing in the $30 billion global video game market.