In case you right click on a printer and delete it, this doesn't get rid of the printer driver from the system. Often when working with print servers and testing several drivers, you need to have to completely get rid of a driver package from the system, so it is possible to install a brand new or a different one.
Windows Vista and Windows 7 has a tool called the Microsoft Management Console (MMC) built into windows which you'll use to delete the drivers completely.
Reboot the computer and login as “Administrator”.
Go to the “start menu”, typing “MMC”, you will see the Microsoft Management Console shortcut appear in the start menu; click on it. (If you haven’t Administrator privilege, you can click right button on it and select “Run as administrator” menu)
Go up to the file menu and select Add/Remove Snap-in…
Then scroll down in the list and select the “Print Management” snap-in and then hit “Add”.
At this screen you are going to want to select “Add the Local Server”, hit Finish, and then hit ok.
Then you can scroll down to your computer name, select the drivers tree and then right click on the driver you want to remove and select “Remove Driver Package”.
Make sure you reboot your machine before trying to add new or different print drivers.