When the driver is assigned to a printer, the the software can't be removed.
If you have removed the printer, it's gone from the User Interface, and you get the error menthioned, then the printer is either still instalked to another profile on the client, or you have a Zombie printer.
Don't be scared, they are easy to hack up to little bits.
What you will see in the registry is the printer name, or GUID name on a client system, with a comma and a number.
On the server, in HKLM\System\CurrentControlSet\Control\Print\Printers\My-Printdriver, 4
This is your Zombie.
Restart the Print Spooler service and the restart will clear out the Zombie.
You can use the PowerShell command restart-service if you need to do this programmatically