A fresh installation of Windows 7 does not support current driver security requirements out of the box, causing the Prolific PL2303GT serial adapter driver to fail with a "Code 52" unsigned driver error. To resolve this, you must manually install specific Microsoft updates (KB3033929, KB3112343, and KB3135445) to enable proper driver signature recognition. Applying these updates allows the Prolific Serial Drivers to install and verify successfully.

Why Windows 7 Fails to Verify the Driver Signature

A fresh installation of Windows 7 64-bit with Service Pack 1 (SP1) lacks support for newer driver security requirements. Because the driver signature is newer than the operating system version, Windows triggers security warnings and "Program Compatibility Assistant" alerts.

It then flags the device with an unsigned driver error in Device Manager until the necessary system updates are applied.

How to Install Prolific Serial Port Drivers on a Windows 7 Fresh Installation

1. Download the required Windows updates (KB3033929KB3033929, KB3112343, and KB3135445KB3135445) on another computer and transfer them to the Windows 7 computer.
2. Run each of these updates following the on-screen instructions.
3. Restart the computer before connecting the USB to serial adapter.
4. After logging back into the desktop, reconnect the serial adapter.
5. Open the Start Menu, search for and launch "Device Manager," and expand the "Ports (COM & LPT)" section.
6. Double-click on the "Prolific PL2303GT USB Serial COM Port" entry to open the properties and verify the adapter is recognized correctly without a "Code 52" unsigned driver error and that the device status shows "This device is working properly".

Applicable To

PL2303-DB9