Currently I am working out a strategy plan to upgrade a printserver which has over 1000 printers hosted. Most of them run on HP UPD PCL 5 v5.3 or PCL 6 5.3. After loading the drivers (choose add driver and located the inf file instead of running install from the directory where you extracted the drivers) I was given the task to bulk update around 400 printers at once. Whell after some digging I found a nice powershell script that will change the driver but! it leaves the printer useless. After you go to properties of a printer it popsup with a nice wizzard that asks you what is my IP address. So the powershell script was useless. After more and more googling I stumbled upon a old version of the HP administration kit from back 2006. Well urm I ain't running windows server 2003 pre SP1 but run a smooth 2008 R2 server. So more digging and guess what I found this site "HP Universal Printer Driver Series for Windows - Resource Kit". This kit also contains the AutoupgradeUPD.exe with a hta file included that doesn't work very good but a excelent command line interface that works like a charm. You can choose to upgrade the old UPD to a new UPD and while upgrading the Autoupgrade.exe will make a sort of temp printqueue with correct ip address were people can continiue to print to while you upgrade the printer. After the upgrade the clients will automaticly download the new drivers and your ready with your migration. Also included is a nice option to log all your options. In my situation one printer will take around 5 to 10 minutes to migrate but it's on a test server that has the same printers hosted but not on such strong hardware as the production server. Mind if you get errors like cannot find the correct driver in the inf file you open the  inf file and on about the bottom you will see the correct name of the driver that is like example: "HP Universal Printing PCL 6 (v5.3). I hope this helps some people in the ICT world migrating a whole lot of printer queues without headage's :)