I use mine with my Palm IIIc. I know this since that's what's plugged into it.
Maybe you can look at what's plugged into it?
Another thought. Maybe your question is a little light. Tell a story. Share an "error message". Share that you were installing "Columbo 3.14156" and "this happened".
And in closing, you don't want to know that TROJAN DIALERS often lock COM1 to their use so when I read such a post I always scan the machine with HOUSECALL (a web based antivirus).
How do I find out what device is using com port 1? I am using XP home addition. thanks for the help