Prolific (PL2303) adapter is an common solution about USB to Serial port adapters.
Even so the company gives their chips only to branded companies.
And the latest Prolific driver, it does one identity recognition at the hardware too.
If the Prolific chip in your adapter is a fake copy, the driver does not work with it.
Currently this chip is also found on the Agilent USB -> IR modems.
And probably in many other old modems that use IR communications like laptops or mobile phones.
About the drivers age , the last made from Prolific was at 2007.
Probably they work fine, and this explains the reason of why they do not update it.
Windows 2000/XP/Server2003 (32 & 64-bit) WDM WHQL Driver: v2.0.16.166
Windows Vista/7/Server2008 (32 & 64-bit) WDF WHQL Driver: v3.3.17.203
http://www.prolific.com.tw/eng/downloads.asp?id=31Prolific has an warning about the fake chips in their website too.
F.A.Q. third question.
http://www.prolific.com.tw/eng/FAQs.asp?ID=50They describe it politely as chip validity and support.
If you ever interested to get an such no-name fake solution from eBay,
be my guest.
But now, you do not have the excuse to say that you was not warned about it !!