Who is the biggest competitor to Windows Server 2003?

Gartner estimates that between 60 to 70% of Windows Server users run NT 4, the grandfather of Windows Server 2003. Microsoft's own estimates are closer to 35%. But 64 case studies released last week suggest the number is much higher. The large number of customers that use NT 4 are in no rush to upgrade to newer software or are in the process of moving to Windows 2000, analysts say, and that could hurt Windows Server 2003 sales for some time.

Gartner estimates that by the end of 2004, as much as one-third of NT 4 users will move to Windows Server 2003. "Two-thirds to 75%" will still be NT 4 customers by the end of next year, said Gartner analyst Tom Bittman. "There's a lot of NT 4 dark matter out there."