We know that many companies are still running production virtual machines with Microsoft W2K3 as a guest operation system. Having statistics for millions of virtual machines we see still today roughly 7%.
But you need to keep in mind that the W2K3 end of support date is approaching fast.
You can read on the official Microsoft website:
What does end of support mean for you? After July 14, Microsoft will no longer issue security updates for any version of Server 2003. If you are still running W2K3 server in your datacenter, you need to take steps now to plan and execute a migration strategy to protect your infrastructure. By migrating to Windows Server 2012 R2, Microsoft Azure or Office 365, you can achieve concrete benefits, including improved performance, reduced maintenance requirements, and increased agility and speed of response to the business.
Furthermore we recommend joining one of the roadshows our partner Entisys is presenting: Skycanvas survival camp 2015 - Windows Server 2003 support
Entisys is using opvizor Health Analyzer as many other partners and customers to check for Windows 2003 VM existence with our customized Inventory report. You can track your efforts to go avoid any Windows Server 2003 support issues very fast.