If you can get the Prolific chip recognized, it will work fine on Windows 8, but I've heard that the programming cables that are often sold with these radios use a counterfeit Prolific chip, so there are really convoluted steps to get them working: http://www.miklor.com/uv5r/UV5R-Drivers.html.  I just use a serial programming cable with a USB->serial adapter with a genuine Prolific chipset (mostly because I already had the required cables from an old radio).