OMNIKEY 3821 driver popups when inserting card

This PINpad installs easily and generally plays nice, but on Windows 7 you get an annoying and unsuccessful attempt to install a driver (with associated popups) every time you insert a card.

This is caused by the Microsoft Smartcard PnP service, which can be disabled by adding the following registry key (Although this is a simple fix, note Microsoft's advice:  This is the least-recommended option. You should use this option only if the cards are legacy cards and there are no plans to implement smart card minidrivers in future.)

HKEY_LOCAL_MACHINE\SOFTWARE\Policies\Microsoft\Windows\ScPnP

EnableScPnP   REG_DWORD   00000000

You'll probably need to reboot as well.

Further reading:
http://www.hidglobal.com/main/technical-support/ 
http://support.microsoft.com/kb/976832
http://lazybit.com/index.php/2010/10/20/smart-card-driver-for-windows-7-popup