Due to fakes, older (not fake!) IC’s made by Prolific are not supported by the current Prolific driver in Windows. Device manager shows PL2303HXA PHASED OUT SINCE 2012. PLEASE CONTACT YOUR SUPPLIER.
Like many I have imported from China, USB to Serial devices with IC’s made by Prolific. Mine are PL2303HX based. And they do not work anymore! Yellow mark in Device Manager, device cannot start. Reason: Prolific made an update to their Windows drivers to fight the fake IC’s coming from China, like FTDI did (see my FTDI unbricking article) and made older devices unusable.
Windows update, which is by default automatic getting the latest drivers, make it impossible to install older drivers, just gets overwritten very fast.
But you can battle this and get the Prolific driver working again. I did this for two PL2303HXA based USB interfaces. Tested with my PL2303HX USB devices and PuTTY serial and a jumper connecting TXD-RXD as loopback to see typed characters coming back in.
Install older driver
Windows 64 bit
1. Download and Save the PL2303 Installer Program here
PL2303_64bit_Installer
2. Unplug all USB-To-Serial adapters and Double click on the installer “PL2303_64bit_Installer.exe”
3. When it prompts you, plug in the PL2303 USB-To-Serial adapter and click “Continue”.
Windows 32 bit
1. Download and Save the PL2303 Installer Program here:
2. Run the installer program. If it offers a choice to remove the driver, then select to remove the current bad driver. Then run the installer again to install the correct driver.
Alternative driver installation:
Easy to solve with an older version of the drive, like in this archive. Unpack in a folder, Update driver, Look on this PC, Have disk, Browse to the folder.
Prevent automatic Windows driver updates.
Windows may ‘update’ the driver again, just rollback the update in Device Manager. For a permanent fix use Group a Policy.
Well described here! Note that this is written for Windows 7, but works fine for Windows 8.1 too.
Windows 10 is more problematic,
Follow one of these guides:
Prevent driver updates via registry (Windows Home)
How to enable gpedit.msc (Group Policy) on Windows Home
Bat file described in above PDF, just download, unzip and execute to get Group Policy on Windows Home 10
How to Prevent Windows from Automatically Updating Specific Drivers