I installed the driver that came with the Prolific USB to serial port and it installed and showed it was working fine but it installed it as comm 3.  We have 2 dual serial ports installed already as comm 2,3,4 and 5.  The pump on comm 3 would no longer work and the USB to serial showed "could not open comm port. I tried to change the comm port and it still would not work. I had to delete the Prolific driver to get comm 3 working again.  Is there a way to install without conflicting with exsisting comm ports?

Hi Allan Ricjards,

If the only purpose is to change the Com Port Number ,please check the following configuration .

Right click the driver ,choose "Properties", " Port Settings", "Advanced","COM Port Number", choose a number that is not in use .

Best regards