Some PC makers are preparing to ship computers and laptops running Microsoft's Windows XP operating system a month ahead of the expected October release date, two major manufacturers confirmed Wednesday. Showing yet another sign of urgency to get its hotly debated software out on the market, the embattled software maker is expected to allow its PC distributors to sell machines running Windows XP as early as September. Microsoft has said the operating system will debut on October 25, but it has seemed increasingly unlikely that the company will reach that date unscathed as legal and industry criticism mounts against the software. Compaq confirmed that it will sell computers with Windows XP installed through its online distribution channel about a month before those computers hit retail shelves in October. "We've known for a while," that Compaq would sell Windows XP computers before October, said David Albritton, a Compaq spokesman. Selling computers with a new operating system before the official launch date is a common practice in the industry, he said. A spokesman for another major computer manufacturer, who asked not to be identified, also confirmed Microsoft's plans to authorize early shipments of PCs with XP installed. He characterized the move as a decision made swiftly, and said that pressure to get the operating system out before critics were able to win a court injunction, which would delay the release, may have contributed to a earlier-than-expected release date. The US Department of Justice and state attorneys general who are plaintiffs in the government's ongoing antitrust case against Microsoft have not filed for an injunction. The software maker has appealed to the US Supreme Court in the antitrust case, a move that some legal experts said could help prevent court-ordered interference with the Windows XP launch by drawing out the legal process. Microsoft, however, strongly denied any plans for an early release. "Our schedule has not changed and we remain on track for an October release," said Jim Cullinan, a Microsoft spokesman for the Windows XP division. "We are on track to release to manufacturers on schedule so that manufacturers and retailers will have PCs ready to sell on the release date." Rob Enderle, an analyst with Giga Information Group, also expressed doubt that customers will be able get their hands on an early copy of the final operating system. "October 25 is when everyone is going to be able to get Windows XP," he said. The move to ship computers running the new operating system early is typical industry practice, he said. Manufacturers use the early shipments to stock their inventory channels so they are ready for the public release date. "Microsoft has a team of lawyers that will sit on top of any (PC maker) who tries to sneak out early releases," Enderle said. Microsoft has also not changed its planned date to ship the Release to Manufacturers (RTM) version of the software, Cullinan said. The company has not said publicly what that date is, though analysts have speculated that PC makers will receive the operating system in its final form in late August. Cullinan did not confirm that time period.