Those applications may themselves be unsupported at this point, the company that built them may be out of business or the in-house development team may have been disbanded. Any of those scenarios would make it difficult or even impossible to update the applications' code to run on a newer version of Windows Server.
Complicating any move is the fact that many of those applications are 32-bit -- and have been kept on Windows Server 2003 for that reason -- and while Windows Server 2012 R2 offers a compatibility mode to run such applications, it's not foolproof.
"Windows Server 2003's end-of-extended-support deadline is really not about an operating system migration/update," said Gillen. "It really is about the entire software ecosystem that remains on Windows Server 2003 today."
It's unlikely that everyone will make the July deadline.
"Most customers understand that some [servers] are not going to make it," said Mayer. "Their best bet is to continue to run [Server 2003] under an extended support model, but before that they should be thinking, 'Let's get that total number down, let's get the easy ones off Windows Server 2003.'"
Microsoft sells after-retirement support contracts, called "Custom Support," to its largest customers, who must have a plan to totally eradicate the unsupported product. Under a Custom Support agreement, Microsoft provides patches only for the security vulnerabilities it has rated "critical," its highest threat ranking.
Because Microsoft charges per system for Custom Support, the fewer Server 2003 systems running at the July cutoff, the less a company will pay.
"But if you have to rewrite apps, that's not going to happen in time," Mayer added.
Vanden Boom's advice was different. "Prioritize," he suggested. "Upgrade those with the most risk to the business first."
Other than a Custom Support contract, neither Mayer or Vanden Boom could recommend a fix for those who won't make the July retirement date, except to press ahead as fast as possible. "We always tell customers to stay in a supported state," said Vanden Boom. Mayer agreed.
Microsoft would like customers facing end of support to shift their servers to the cloud, specifically the Redmond, Wash. company's Azure cloud-based platform.
But while Vanden Boom thought it was still possible for some customers to make both moves in time -- drop Windows Server 2003 and transition those systems to Azure or a competitor, like Amazon's AWS -- Mayer believed it best if companies took a more measured, step-by-step approach.
"Most customers have done it as two separate moves," said Mayer, hinting that it was too much to bite off at once.
Sign up for MIS Asia eNewsletters.