The newer USB-1 cable works right out of the packaging, no need to download drivers. If you have an older cable like I do follow the directions I have layed out below to get your cable working on Windows 8. If you need the installer let me know and I can upload it to my server.
I'm using Prolific PL2303 Driver Installer v1.5.0
After you install go into your Windows Control Panel, open the device manager, plug the USB-1 cable in.
You should immediately see Prolific pop-up with a caution flag under 'Ports (COM & LPT)'
Right click on 'Prolific USB-to-Serial Comm Port'
Click 'Properties'
Update Driver
Browse my computer for driver software
Let me pick from a list of device drivers on my computer
Select 3.4.25.218 [10/7/2011]