I've played with a couple of different USB to Serial converters, and eventually dumped them in favor of a small docking station/port replicator. It's a little more bulky, but you get a true serial port that way.... Something like this.....
I called tech support and we eneded up reinstalling XPpro without the HP drivers. I installed the USB to serial drivers. All ,the cables I had inhouse, loaded fine and worked great. Then I installed the HP driver/application disk. All the USB to serial cables drivers stayed intact but one. LiFe is good once again in the controls world. Thanks for the ideas.
Thanks for the follow up note. I am 100% sure it will benefit someone in the future. It's nice to have closure. I wish the closure rate were higher here. An unsolved puzzle bugs the heck out of me. It's like watching 3/4 of a mystery movie, then the power goes out ...
It's too bad many so posters don't take the time to follow up here as you did.