Matt,

I had the same problem. My cable was on COM13 and everything below was already
in use. Hopefully I can explain what I did to eventually move mine to COM3. So
let's get started...

First plug in your programming cable.

Then launch Device Manager. I get there by going "Start" | right click
"Computer" | "Properties" | "Device Manager"

Expand "Ports (COM & LPT)". This should show your currently active COM ports
including your programming cable. I should show up something like "Prolific
USB-to-Serial Comm Port (COM12)"

Now double click the programming cable entry and then select "Port Settings" |
"Advanced". Now click the "COMM Port Number" button and you should see a long
list of ports.

If there is a COM number between 1 and 8 inclusive that is not marked "(in
use)", select it. Launch you programming software, configure the same port and
try it. If it works, your done. If not, come back to here.

My guess is that everything listed with a number less than 12 is shown as "(in
use)". I'll also bet that some of the smaller COM port numbers are missing from
the list. You can't see them because they are hidden. But if they are hidden,
how do we know what they are and how do we decide if we can do without them?

You probably didn't need to do the above. I thought it was an important exercise
to show you why we are doing the rest. Let's continue...

OK. Now we need to launch a Command Promt. But not a regular command prompt
(this was missing on several of the pages I googled to figure out how to do
this). Click on "Start" | "All Programs" | "Accessories" | right click on
"Command Prompt" | "Run as administrator".

Enter "set devmgr_show_nonpresent_devices=1" (without the quotes) into Command
Prompt and then press "Enter" (I used cut and paste to put the text into the
Command Prompt window).

Now go back to Device Manager and at the menu bar at the top select "View" |
"Show hidden devices".

Now look at your expanded "Ports (COM & LPT)" and you should see the hidden
ports in the tree as well.

Now hopefully you will recognize a device/port from 1 through 8 that you don't
really need and can delete, or even better, move to a higher com port if it is
capable of working on a higher number. I deleted com ports that were (in use)
for an old wireless phone I no longer use.

Now double click on the Prolific driver and click the "COMM Port Number" button
again and change the com port to the com port you just freed up.

Now you should be able to launch your programming software, select the same
port, and start programming.

Hopefully I explained this well enough that you can figure out what I didn't
explain well. Good luck.

73,
Jim KC9HI