P38 2.5D Faultmate serial to usb

When I bought my Faultmate Extreme a few years ago I also bought Toughbook laptop with it which came with the software already loaded and had a 9 pin serial port. I have now loaded the software in my modern laptop which has no serial port. I have bought a serial to usb conversion cable but still have to select a comm port from the dropdown menu. The port varies with whatever usb port I am using. I experienced a similar prob with my EAS software and cable which I had bought from Datatek and similarly swapped to serial>usb convertor .
I emphasise that this is absolutely no criticism of either of these fine pieces of kit but rather an admission of my own shortcomings. Does anybody have experience of transferring Faultmate to USB and another computer........I might be just being thick.

If you go into device manager and find the USB to serial converter you can force it to use COM1 in the settings then it SHOULD be OK.
However, not all USB to serial converters are created equal and some work better than others. In my experience, the ones with FTDI chipset on them work best.
Hope that helps.