Unable to upgrade and receiving 0x8007232b error code

Hi,
I am currently using Windows Server 2003 as the server operating system.
I want to use Windows Server 2008 as it has many advanced features.
I know the basic process of upgrading and I goggled and came to know that we need a KMS server for upgrading.
But I am unable to upgrade and receiving 0x8007232b error code.
Please fix this bug so that I can use the advanced features of Windows Server 2008.
Thank you
