Windows Server 2008 (build 6003) cannot in-place upgrade to Windows Server 2012 R2 or higher. You must perform a (fresh install + app reinstallation) or use a tool like Azure Migrate if moving to the cloud.
The kernel file ( ntoskrnl.exe ) version remained 6.0.6002.xxxxx. Thus, but a versioning inconsistency. windows server 2008 build 6003 patched
: (If 64-bit) The initial release of Microsoft's native hypervisor for virtualization. Windows Server 2008 (build 6003) cannot in-place upgrade
This was it. The final security rollup. The legendary "Build 6003" patch. It was the cumulative update released just as Microsoft pulled the plug on mainstream support windows server 2008 build 6003 patched