I have WinXP on a laptop with an internal IrDA port... it used to work fine (too fine, actually..whenever my Palm was anywhere near the computer the Wireless Link would spring to life), and now it's completely disabled. One thing I did try to do inbetween was install IrCOMM2k, which didn't help me, so I removed it.
I removed all the virtual and IR-related COM ports, also in the msports file. Device Manager reports that "Built-in Infrared Device" is enabled and "working properly", yet it is utterly unfunctional; no application can access it and testing the port with an external device reports "no IrDA devices in range".
Of course, I try uninstalling and reinstalling this standard WinXP IR driver several times.