According to sources familiar with the company's plans, Microsoft will be giving product reviewers access to Windows Vista Release Candidate 1 (RC1) as soon as today.

The first release candidate (effectively a public beta) of the software seems set to ship on 5 September. The public beta will aim to expose any remaining flaws in the code.

"It's like throwing one of those roach bombs in an empty apartment and see what comes out," said Joe Wilcox, an analyst with Jupiter Research. "They're looking to see if there any bugs hiding in the walls somewhere."

Wilcox said it's likely Windows Vista will have at least two release candidates. If this is the case, the company could make its target deadline of releasing Vista to business customers in November, and consumers in January 2007.

However, if Vista requires a third release candidate because of any problems or bugs that come up during the final testing period, "no way" will Microsoft hit its current deadlines, he said.

With the last major upgrade to Windows, Windows XP, it was "not quite" two months between RC1 and the product's release to manufacturing, Wilcox said. If Microsoft indeed releases Windows Vista RC1 on 5 September or thereabouts, the release to manufacturing - and a release to business customers - could happen as soon as early November. Microsoft has said it will release Vista to business customers in November, but has not specified at what time of the month.

OEMs (original equipment manufacturers) typically need about six weeks to get the OS installed and tested on PCs before putting those machines on the market, so if Windows Vista makes it to manufacturing by the end of November, it could hit its January release date for consumers.

Again, Microsoft has not specified exactly when in January Vista will make its debut, though some speculate the company may want to make a big splash with Vista at the annual Consumer Electronics Show (CES) in Las Vegas. CES 2007 is scheduled for 8-11 January.

Microsoft in March pushed back the release date of Windows Vista to November for business users and January 2007 for consumers. However, analysts suspect the release may slip further.