On Monday it revised its Custom Support Agreement (CSA) program, which extends support for legacy products that business customers continue to use.

Due to a new per-device pricing structure – a change from the former flat-fee structure – pricing could become more expensive, said Ines Vargas, Microsoft support policy director.

But she said customers that don't have a lot of hardware devices running legacy Microsoft software could save money with the pricing changes.

Products affected by the changes include Windows NT 4, Exchange Server 5.5 and Windows XP SP1. Windows NT 4 will be entering its fourth year of CSA support in January 2007, with Exchange 5.5 entering its second year. Windows XP SP1 will enter its first year of CSA support next month.

Microsoft started the CSA program two years ago, typically giving customers five years of mainstream support, while offering business customers the option of purchasing extended support for five further years.

Microsoft will make CSA pricing available for the next three years to customers who take part in the program so they can budget for support if they plan to continue having legacy products in their IT environments, Vargas said. Previously, customers knew only for about a year how much they would pay for support through the CSA program, she said.

"This is all about providing customers with choices and to [help] the planning and budgeting process," she said.

Microsoft does not publicly disclose the CSA pricing, but Vargas said pricing does go up each year to keep up with growing support costs for older software.

And only customers with its high-end managed support offering for large enterprise customers, Microsoft Premier, can take part in the CSA program.

Vargas said she does not believe making changes to the CSA program will drive customers to migrate to more current versions of legacy software, even if it means paying more to support older products.