Thank you for contacting Plugable with your question. I’m here to help you with it.
An access is denied error means that your computer is trying to access or change a file, but does not have permission to do so.
In the driver folder you downloaded, right-click on the PL2303_Prolific_DriverInstaller_v1.7.0 icon, then select Run as Administrator.
If that doesn’t work, it is possible that your user account has been blocked from making the necessary change. Is this computer at a company or institution and administered by the IT staff? They may have to do the installation or change the permissions. Otherwise, it is possible that an anti-virus or other program is blocking the changes.
Please try the above and let me know how it goes.