Limited support will continue for legacy software, such as Windows NT, under modified Custom Support Agreements (CSAs). The announced changes enable companies to stay longer on existing software products, if they are willing to pay a potentially high per-desktop charge.

CSAs are the final stage of Microsoft's product support life cycle. Customers require CSAs to get support from Microsoft for products that have left the Extended support phase, which ends seven to ten years after the software's release. Services covered in a CSA include the following:

• Problem resolution
• Security hotfixes for "critical" and "important" vulnerabilities
• Access to all hotfixes produced during the Mainstream support phase
• Ability to request nonsecurity hotfixes for new bugs (for an additional fee).

When Microsoft introduced CSAs, the company emphasized that they would be available for only specific products (initially Windows NT 4.0 and some embedded products, with Exchange 5.5 added in 2006), and would likely terminate at the end of 2006. The company now says that some customers have been unable to migrate off the older software completely, and as a result, it will continue to offer CSAs.

Microsoft has not disclosed pricing for CSAs, but they will now be priced on a per-computer basis; previously, CSAs offered an organization blanket coverage for a given product. The new CSA terms give customers more flexibility as well as an incentive to migrate off of legacy software—the cost of a CSA will go down for each computer migrated off legacy software.

Microsoft has not set an end date for CSA coverage. However, the price to cover a product will rise each year as the product ages and Microsoft's cost to support it increases.

For more information about support for legacy products, see "Support Life Cycle Extended for NT, Exchange 5.5" on page 25 of the May 2005 Update.