Microsoft originally said that support for NT 4.0 would end this month. Businesses could either upgrade to Windows Server 2003 or pay for a custom support contract up to December 2005.
After calls from larger firms for more time to upgrade, Microsoft agreed to extend custom support until December 2006.
Peter Houston, Microsoft's Windows serviceability senior director, said, "To ease migration, we have decided to run the custom support program until 31 December 2006 and charge the same amount as we will in 2005."
Microsoft also announced that support for Exchange Server 5.5 will finish at the end of 2005, but that there will be two years of custom support. It will end support completely in December 2007.