HI Manjappa,
I would say that this is becuase windows server 2003 is already out of support.
But you can take decision if you want to continue with same OS or want to have
supported OS. Please note that in case you are using windows server 2003 which is
already out of support in that case you might not get the support so I strongly recommend to
use supported OS version. Howevere if it is only for learning and system will not be a productive
system then you might continue and check if you are able ti install the system with WIndows Server
2003 without any issue.
You might check windows site to get what version 5.2 , 6.0 etc means .
5.2 --> Windows Server 2003
I hope it helps.
Best Regards,
Gaurav