OK. You never create standalone servers. I know. But, let’s just say you *did* have one, maybe for development or test, and let’s say you had such an environment on your laptop, and also let’s say your machine had an embarrassing name that you needed to change before you next demoed SharePoint stuff on it… OK, you get the picture. 
The Microsoft recommended steps are:
- Rename your PC using Computer properties:
- Reboot.
- Run the PowerShell Command “Rename-SPServer”
There is only one problem with this suggested method: it’s a steaming pile of nonsense.
The correct procedure would be:
- Rename your server using “Rename-SPServer”
- Rename the PC using Computer properties
- Reboot
- Rename your SQL instances
- Restart SQL
- iisreset /noforce
If you are unlucky enough to have tried to follow the official guidelines and renamed the PC before executing Rename-SPServer, you would get a message like this when trying to launch the SharePoint Management Shell:
Then the correct recovery would be:
- Rename the server using “stsadm -o renameserver”
- iisreset /noforce
- Rename your SQL instances.
- Restart SQL
- iisreset /noforce
Best of luck!