I recently needed to rename a Hyper-V server (which is essentially a server core install of Windows Server 2008 R2). It took so doing, but I found the command.
Netdom renamecomputer oldname /newname:newname /userd:someuser /passwordd:*
Replace the computer names with valid ones and a domain admin user, and the command will prompt for your password. That’s it, reboot and you’re set!