You don't need PL-2303 USB-to-Serial software in order to install your RS 232 device. Navigate to the Downloads section of the official web page, scroll down to USB to Serial RS232 tab and click the Drivers button next to Prolific PL2303. After that, save the file to your computer and unzip the installation package using WinRAR or WinZip. Next, connect your RS 232 device to your computer, and check the No box from the Found New Hardware Wizard. Select the Install from a list or a specific location (Advanced) option, click Next, and use the Browse option to navigate to the installation package. Select the drivers and install them following the on-screen instructions. After that, reboot your PC and press Scan for hardware changes icon from Device Manager.