Reboot your XP machine into Windows Safe Mode (or Safe Mode with Networking).
[Press F8 during the windows boot up progress bar to select which boot mode to come up in].

This will eliminate a lot of problems in one go.
then try and run Empldoe then to fix/upgrade your empeg.
You can then assign it a IP address so that you can then use the Ethernet in the future if neeed].

If the com port won't work under Safe mode then you really need to find another PC with a known usable com port you can use to fix the empeg problem.

Assuming it does work under Safe mode, then you have a 'work around', you can then compare whats running in Safe mode versus whats running in normal mode and try and locate the difference.

Be aware that the UPS service uses a COM port and your Dell may think you have a UPS installed - this can be turned off under the Power setting in Control panel.

Sorrry I can't be more helpful than the above suggestion, but I run XP on a Dell PC at home with Hyperterminal and can use my com ports without problems, I have to make sure I know which device is plugged into what com port as I have about 5 com ports on my system now.