San Francisco  - Microsoft officially retired Windows XP on Monday, forcing buyers of new computers to go with the operating system's unpopular successor Windows Vista.

The retirement affects copied of XP sold to large computer makers and stores. Consumers will still be able to get XP while in-store stocks last, or from small computer assemblers who will be allowed to continue using the veteran system until the end of January 2009.

Microsoft is allowing the makers of ultra-light, low-cost laptops to install XP through January 2010.

Windows Vista has sold more than 140 million copies since its January 2007 release, but the vast majority of copies have been pre- installed on new PCs. Millions of buyers have reportedly downgraded their systems to install XP, while business adoption of Vista has been slow despite its greater security features and increased graphics power.

Vista's problems started at launch with many users complaining of performance glitches and problems when running the operating system on computers other than the very fastest, high-end machines.

XP was introduced in 2001, and tech magazine InfoWorld said Monday that it had collected 210,000 signatures on a petition to Microsoft for a stay of execution on XP.

For instance, Intel, the chipmaker that has long been Microsoft's partner in dominating the PC industry, says that while it is testing Vista "in some departments," it still uses XP.

"We have not deployed Vista across the enterprise," Intel spokesman Bill Calder told the San Francisco Chronicle.

Even though XP will no longer be officially available, many companies will not be forced to accept Vista, as they have downgrade rights allowing them to install XP, even as they pay the price for the newer operating system.

Many companies are expected to wait to upgrade their computers until 2010, when a completely new operating system called Windows 7 will become available. (dpa)