Ever noticed that on a 2008 print server you install a HP LaserJet 4xxx driver on it but when you open the properties page of the printer you still get the error that the driver wasn’t installed and if you want to install it? I’ve run into it while working on a Citrix Universal Print Server issue and a colleague pointed this out to me (thanks to Kristof Peeters).
This is a known bug in 2008 and Microsoft hasn’t fixed this yet for some reason unknown to us peeps…
Here’s a workaround to get this annoying message out of the way.
Caution! Using Registry Editor incorrectly can cause serious problems that might require you to reinstall your operating system. Citrix cannot guarantee that problems resulting from the incorrect use of Registry Editor can be solved. Use Registry Editor at your own risk. Be sure to back up the registry before you edit it.
Start the registry editor and navigate to the following path:
HKEY_LOCAL_MACHINESYSTEMCurrentControlSetControlPrintPrinters<name of the printer>PrinterDriverData and change the key HPTrayCount from “0”(zero) to “8”.
Close the registry editor and go back to the printer and open the printer properties.
You won’t see the error message popping up. When you change the driver to another HP LaserJet 4xxx version you will see this error back, so you need to change the value again back to “8”.
Hope this helps 
.