NEC Express5800/120Rh-2 N8100-1126F - Manual (Page 366)

E-4 Installing Windows Server 2003
About the Upgrade to Windows Server 2003 R2
The "in-place upgrade" from Windows Server 2003 to Windows Server 2003 R2 is not
recommended because it may overwrite any files or registries, and cause unexpected impact to the
system or the applications.
If you install Windows Server 2003 R2, backup user data referring "Windows Server 2003 Clean
Installation", and reinstall Windows Server 2003 R2.
NOTE: "in-place upgrade" is to perform overwrite upgrade from
Windows Server 2003 which already installed to Windows Server 2003
R2.