I also had this problem and searched the forum using the keyword EComPort but didn't find any thread with the exact solution that worked for me som I'm posting the solution here since this thread described the problem well.
My computer does not have a physical com-port as it is a fairly new one. This means I got that same error message sven reported.
I have a USB-attached radio simulator that I bought rather cheaply at a faire so I don't need to have it attached to a COM or LPT port.
I solved it like this:
1. Open control panel (in classic mode) and choose Add new hardware.
2. Click Next, then "Yes, I've already attached the new hardware", then Next again.
3. Scroll down to the bottom, click "Add new hardware" (or something similar), then click Next.
4. "Choose manually from a list", then click Next.
5. Choose Ports (COM & LPT), click Next.
6. In the left part, choose (Standard port types), in the right part, choose Communications port. Click Next and then Next again.
7. You'll get a message saying the device is installed but may not be working. (Obviously since we really didn't add any hardware.) Click Finish.
8. Open the device manager by holding down the Windows logo key and pressing the Break button on your keyboard. Select the Hardware (or is it Devices?) tab and then click the button Device manager.
9. Scroll down to Ports (COM & LPT) and expand it. You should now see a Communications port with a yellow and black ! on it. In parenthesis it should say the number this Com-port now has in your system. For me it is (COM4).
10. Open up notepad (or your favourit text editor). And paste in the following:
- Code: Select all
Windows Registry Editor Version 5.00
[HKEY_LOCAL_MACHINE\HARDWARE\DEVICEMAP\SERIALCOMM]
"\\Device\\Serial0"="COM4"
Then replace the COM4 at the end with your Com-ports number like "COM1" if it should differ.
11. Save the file as fms_com_port_fix.reg on your desktop (or wherever you like).
12. Go to your desktop and double-click the file. Approve any security warnings your system may give you.
That should be it, FMS should now start for you.
Note: I'm using a Swedish version of Win XP Pro so the names of buttons and texts above in English may not be 100% correct.
I'm happy with FMS, it works nicely for me and I've already had a few hours of flying in it and crashing thousands and thousands of Euros worth of airplanes

(Yes I'm a noob at flying R/C)