I was working on this problem for one of our Fort Myers Business Tech Support Clients, but I’ve had this problem a couple times and the solution seems to be slightly different each time. The problem presents itself as a Device in Device Manager showing “”The Device Cannot Start (Code 10)” after you’ve installed the Prolific PL-2303 Drivers from the Prolific website. Which are available here: http://www.prolific.com.tw/eng/downloads.asp?ID=31
The solution is to use a similar driver set floating around on the internet here: http://www.usglobalsat.com/download/546/win_drivers.zip
Unzip the file and install the executable within. That fix solved the problem for me instantly. To make sure that the new driver take priority over the other one in Windows 7 right click on the device and go to Unistall and check “Delete the driver software for this device”. I found this solution on the microsoft social forums here.