With its most directly affected customers, Microsoft is taking a carrot-and-stick approach on the upgrade issue. The company is promising to indemnify customers from third-party claims if they upgrade quickly. But Microsoft also noted that its contracts require users to "immediately" upgrade to new noninfringing software that it releases. Existing users who have mixed Office XP or Office 2003 with Access can't ignore the upgrade issue completely. Microsoft is recommending, but not requiring, that such users upgrade their systems.

That's not enough to prompt Marc West, CIO at Kansas City, Mo.-based H&R Block Inc., to rush to upgrade the tax-return preparation firm's PCs. West oversees about 120,000 Windows systems in 14,000 offices nationwide, and he said that most already run Office 2003 or Office XP.

Although convincing customers to install the non-infringing code "is of value to Microsoft, it's not of direct value to us," West said. "We will most likely continue on our normal path unless security issues arise."

"Companies have no financial incentive [to upgrade] unless they are going to be financially dinged," McGrew said. "Most will just do it at their own pace."

Microsoft noted that for small businesses, installing a service pack or patch is relatively painless. It's also less trouble for corporate users if it can be combined with an Office upgrade. But analysts said the required additions could dissuade some users on older versions from upgrading now, especially with a new Office 12 release due later this year.