Thanks Josuetas, I think I understand what you are saying.

What I found very confusing was that parts of MCS worked on the Sony Vaio but other parts of MCS did not work. For example, the MCS Serial Communicator worked as did TeraTerm which is my preferred serial terminal emulator program but the MCS Loader did not work at all.

I think I am right in saying that MCS Serial Communicator and TeraTerm do not check what ports are available, they just assume COM1 will always be available and mostly it is.

MCS Loader on the other hand uses a windows API call to access a COM port. Windows manages the VCP BUT not all USB to Serial adapters handle the com port assignment correctly.

I had an IT guy look at my Sony Vaio problem. A search through Registry showed only COM4 and COM5 had entries - not COM1 or COM2. He added a new registry key as follows.

In Hkey_local_machine\hardware\devicemap\serialcom was added a string "COM1"

The USB to Serial converter I have is by "Magic Communications Technology" - a dodgy name if nothing else.

It now works but only after a manual entry for COM1 was added to registry and one further gotcha is covered.

There appears to be another problem with the Sony Vaio. If there is any activity on the USB/Serial port during boot up, the Sony will interpret this as mouse activity and then assigns the mouse to the USB port. Any attempts to use the serial port sends the cursor scurrying all over the screen. What I must do at boot up is remove the USB connector, let the machine complete the boot, then attach the USB/Serial adapter, then start MCS.

Not quite plug and play but eventually workable.

Thanks to those that sent me suggestions.

Cheers
Brian