WIN NT4 SP6 – ActiveSync can’t find COM1

I am using windows nt4 sp6 and microsoft activesync. I have a IBM Thinkpad 600x Active Sync cannot find COM1. Apparently COM1 is being used by some other device. But I can’t locate it. My Modem is on COM2, and the IR port is disabled. Is there any way I can determine what is using a COM port ?