The Dell should be factory set to AUTO in the BIOS. Unless you have changed it yourself, so I doubt that would be the cause.
I'm going to ASSUME, you are refering to the model MK19A. In which case I could not find ANYTHING for the Windows XP OS, except something about switching from the serial port to a PS/2 port and plugging the mouse into the supplied serial port on the reciever with the included adapter.
God, you gotta hate hardware manufacturers that sell something and KNOW it will have issues with some PC's, but we'll leave that discussion for Bobs OTHER php board.
Anyway. I'm almost 100% convinced now that the problem is with your mouse.
That series of Dell, I believe, comes with an adapter on the mouse end (green) that will unplug and allow you to use the mouse on a USB port instead.
I'd try that method and see if you can get it working. Plug the MOUSE into the USB port and don't use the PS/2 port (if that is in fact an option). Your serial port and ps/2 port are I'm guessing on the same IRQ.
If this is not an option, then goto the device manager, communications port, then right click and then goto PROPERTIES, then click the RESOURCES tab, UNCHECK "USE AUTOMATIC SETTINGS" and assign the IRQ to an unused/non conflicting IRQ,.
Also, I'm not sure about this so don't quote me, SOME devices will have communication problems on a COM port if there BAUD rate is set too low/too high. But lets not mess with that setting until we have tried other things first, in XP, thats more of a desperation move and can usually be pointless.
Another point I want to make, is from what I have seen, I did not see anything about that remote being XP compatible. Unless I missed something on the x10 website, or have incorrectly identified the remote you are using.(I did guess).
But anyways, after the IRQ change, reboot and see if your then getting communications.
I'm not sure what else to tell you at this point, as I am not familiar with x10's products and am only giving you a general reference to most ANY serial device.
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