When you enable the protected mode in Windows Internet Explorer 7 on a Windows Vista-based computer, you cannot connect to a shared printer by using Internet Explorer 7.
This behavior occurs because some registry subkeys are restricted when you enable protected mode in Internet Explorer 7. The registry subkeys make sure that you can connect to a shared printer by using Internet Explorer 7.
Note By default, protected mode is enabled in Internet Explorer 7.
To work around this behavior, connect to a shared printer by using the Add Printer Wizard.
Steps to reproduce this behavior
Start Internet Explorer 7, and then type http://<servername>/<printers> in the Address bar.
Select a printer, and then click Connect under Printer Actions.
In this case, you cannot connect to a shared printer.