DO NOT USE THE DRIVER CD from the USB-RS232 adapter box. (only as a last chance after you tried everything else without luck, but that should never happen). The driver from the adapter-cable CD is likely to cause you many problems.

Recommended Driver

Most of the WINDOWS drivers released by prolific over the years were seriously broken. What's worse, they seemed to work with TerminalProgram, and under some circumstances (not sending too much data at a time, waiting a lot, etc...).

Prolific windows-XP driver version (2005-07-25) is broken without any doubt.. Verify in the device manager / com ports / properties that you do not have this.

The broken 2003-2005 drivers are more common than one would think, included on many CD's even several years after prolific found out it's broken and fixed in new releases. Somehow the information did not make it to the 10 cable manufacturers prolific sells millions of these (HW-wise great!) chips. Maybe it's a good idea to notify manufacturers who purchase millions of these chips with broken drivers released. That way they would learn about the situation and the need to upgrade driver (it takes 3 minutes for an enduser to upgrade after 500 mins of headache caused by apparently application problems, and maybe 0.01 min / sold cable for the manufacturer to update the zipfile on the CD). Unfortunately the notification either didn't happen, or was unsuccessful.

  • we contacted prolific about the PL2303 driver when we were only 99% sure that the XP driver was broken, but we never received a reply. Now that we met more cases, made more investigations and know for 100%, fortunately prolific has a newer driver for download that works so much better.

Your driver might be broken even if it works for some applications, or work "sometimes". In many cases it appeared that VemsTune communication was bad when in fact the prolific windows driver lost data and reported bad about the buffers.

Sorry about the inconvenience. If you use the recommended driver, and still have communication problems, make sure to report windows and driver version as well. Only saying that "the cable works with ... app and not with ... is not enough information".

I have a slightly different cable but still with the Prolific chip, and the new driver does not run at all. Even tried cleaning out the registry to make sure no remains of the old driver was left. Tested on 3 computers (one Vista and two XP) with no luck. The old driver "Prolific windows-XP driver version (2005-07-25)" works on all 3 without any problems at all.

I had trouble with freezed MT with suggested new driver.

Old driver looks better to me:


After testing a lot of drivers for WIN7 x64 this driver seems to work just fine at my computer:

It`s released: 12.04.2010