[Dx4win] Com 1/ antenna rotator help

[Les Kalmus]

I am having a problem with DX4WIN controlling my rotator. I made my 
backup PC my primary for radio.
On this PC I can't control the antenna rotator like I did on the other PC.
The rotator is on COM1 which I think is in use by something since I am 
having the same problem with N1MM.
All the DX4WIN settings are the same as they were on the other PC, etc.

Can anyone tell me how I can determine what program is using COM1?
I also cannot connect to it with HyperTerminal which says it's in use.

Is there software available which can figure it out or are there some 
tricks in the registry which will point to the culprit?

Les W2LK