Microsoft said Monday it would offer free technical support to small businesses that buy new PCs with Windows Vista in the next three months, its latest attempt to convince users that moving to Vista is a good idea.

And if those efforts are for naught, Microsoft will help those users downgrade from Vista to Windows XP, the same maneuver several large computer makers, including Dell and Hewlett-Packard, have used in recent months to continue offering the older operating system to buyers.

The offer, dubbed Windows Vista Small Business Assurance, is available to businesses with fewer than 50 employees or 25 PCs, and it provides free telephone support through the end of October to companies that buy new PCs with Vista Business or Vista Ultimate between now and Sept. 30, according to details posted on the Microsoft Web site.

Only businesses buying new hardware can take advantage of the free support; companies upgrading existing computers from, say, Windows XP, don't qualify.

Microsoft has set up a toll-free number that will be manned weekdays from 10 a.m. to 7 p.m. PDT. Typically, Microsoft shunts users to computer manufacturers for operating system support.

"We have such confidence in the state of Windows Vista that we're going to all U.S.-based small businesses and we're offering free support, one-on-one coaching and assistance via phone to help them go through and make the transition to Windows Vista," Brad Brooks, the executive who heads Windows consumer marketing, said in a keynote address at Microsoft's Worldwide Partner Conference yesterday.

Brooks also acknowledged the problems, real and perceived, that users have had with Vista since its general release early last year. "We had an ambitious plan. We made some significant investments around security in this product," said Brooks. "And you know what, those investments, they broke some things. They broke a lot of things. We know that."

But Decisions on Microsoft analyst Michael Cherry questioned whether free support will convince users to switch. "It will give some people a safety net," he said, "but if you have a machine truly configured for Vista, you probably like Vista. My biggest problem is still the hardware footprint for Vista."

To make his point, Cherry quoted from a catalog he'd recently received from a "major OEM," a reseller that targeted small and midsize businesses. On the cover, he said, was a PC priced at $500 that includes 1GB of memory. "I don't see that as being really adequate to the task," said Cherry. "But the base for all the systems [in the catalog] seems to be 1GB. I still worry about the amount of RAM in machines being sold with Vista."

Small businesses aren't putting off Vista because they think they'll need more hand-holding, or even because they believe compatibility issues plague the operating system. "There's some compatibility problems, but those are kind of being resolved," said Cherry. "That's not their fear. Their fear is spending that much money on hardware for a PC that can run Vista."

Microsoft's help desk representatives will answer any Vista questions, help users with application and peripheral compatibility problems, and point out key features of the operating system, said the company. The support isn't permanent; it ends Oct. 31.

The program, said Microsoft, is only temporary because it's designed to help customers make the transition to Windows Vista. "As Windows XP availability begins to wind down, we want small businesses to know we're behind them to provide special support during this transition period," said Microsoft in the program's online FAQ.

But if Small Business Assurance can't make users happy, Microsoft will walk them through a downgrade to Windows XP. "In cases where a small business customer cannot overcome an incompatibility issue and has the PC's recovery media disc for Windows XP, we are equipped to help with a downgrade over the phone," said Microsoft on its Web site.

Small Business Assurance is available only to U.S. customers, although Microsoft didn't say whether it might expand the program into other markets.