Microsoft has announced that it will be launching its Games for Windows - Live gaming service on 18 May to coincide with the launch of Halo 2 on the PC.

The new service will allow PC gamers to compete online against eachother and in June compete directly against Xbox LIVE gamers.

Available only to Windows Vista users, Games for Windows - LIVE will connect Windows gamers to over six million gamers already in the Xbox LIVE community.

Shadowrun, launching in June will for the first time connect Windows gamers with Xbox 360 players in cross-platform matches using a single service.

UNO, the classic card game, releasing later in 2007, will also support cross-platform play between Windows and Xbox 360.

The launch of Games for Windows - LIVE also marks a major expansion of the Xbox LIVE service across multiple platforms, uniting gamers with a single identity, a single gamertag, a single friends list and a single list of achievements attainable on the Xbox 360 and a Windows-based PC.

As a unified service with Xbox LIVE, Games for Windows - LIVE will be available in every country and region supported today by Xbox LIVE.

“Five years ago, we began building a service that now defines the bar for online gameplay”, said Peter Moore, corporate vice president of the Interactive Entertainment Business in the Entertainment and Devices Division at Microsoft.

Members of Xbox LIVE automatically receive the functionality of Games for Windows — LIVE, using the same gamertag and friends list at no additional cost.

Like Xbox Live Microsoft is offering both Silver and Gold memberships. There is no cost associated with signing up for a Silver membership and current Xbox LIVE Gold members will automatically have access to Gold features on Games for Windows — LIVE titles.