PGP Desktop for Windows has been tested with the following personal firewall software:
The Zone Alarm firewall, by default, restricts access to localhost. Because PGP Desktop redirects connections to localhost, this stops PGP Desktop from working correctly. To fix this, add localhost (127.0.0.1) as a trusted IP address in Zone Alarm (on the Firewall/Zones screen). Email proxying by PGP Desktop will work normally once this is accomplished. 
PGP Desktop 9.12 is not compatible with InfoExpress CyberArmor Personal Firewall versions 2.6.050802 or 3.2.050802 or prior. Before you install PGP Desktop, you must upgrade these versions: contact your helpline or the vendor (InfoExpress at firstname.lastname@example.org) for more information. 
: PGP Desktop is compatible with Webroot Desktop Firewall Version 5.8 only. Earlier versions of Webroot software are not compatible with PGP Desktop.
PGP Desktop for Windows has been tested with the following terminal services software:
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Citrix Presentation Server 4.0 Citrix Metaframe XP Windows 2003 Terminal Services
The following features of PGP Desktop for Windows are available in these environments, as specified:
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Email encryption is fully supported. PGP Zip functionality is fully supported. PGP Shred functionality is fully supported. PGP NetShare is fully supported.
PGP Virtual Disks cannot be mounted at a drive letter over Citrix/TS, but can be mounted at directory mount points on NTFS volumes.
PGP Whole Disk Encryption is not supported. Smart cards are not supported.
For information on how to install PGP Desktop on a Citrix server, see PGP Support KB Article 832 (https://support.pgp.com/?faq=832).
This section describes the system requirements (compatible smart cards/tokens and readers).
The following smart card readers are compatible when communicating to a smart card at pre-boot time. These readers can be used with any compatible removable smart card (it is not necessary to use the same brand of smart card and reader).
Most CCID smart card readers are compatible. The following readers have been tested by PGP Corporation:
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OMNIKEY CardMan 3121 USB for desktop systems (076b:3021) OMNIKEY CardMan 6121 USB for mobile systems (076b:6622) ActivIdentity USB 2.0 reader (09c3:0008) SCM Microsystem Smart Card Reader model SCR3311