I've been having this hell of a problem. A HP5200 laser printer will continue to print until there are no trees left, on its current PCL6 drivers. I have a different set of PS drivers I want to use.
I have tried
* updating the driver
* uninstalling the printer
* uninstalling all the USB drivers that could associate
* removing the driver physically
* installing the new driver over the top
* using driver removal software
* physically removing all links to the driver in the registry
* combinations of the above in sequence
but when all is said and done and I plug the printer into the machine the PCL6 driver re-installs itself. So then I decided to remove the driver physically from the system driver store so it cannot possibly happen, but Windows says I need SYSTEM privilege to to this (good on ya MS), so that is a no go also.