OTR,
As you said you youhad unloaded the driver, I assume you know how to access Device Manager. In case you don't, for Windows XP hold down the Windows key and press Pause. Click on the Hardware tab and then Device Manager button. Click the + sign next to Ports (COM & LPT) to expand that section. When you plug in your GPS to a USB port, you should see ONE COM port added with a name associated with the driver for your GPS.
You might try clicking 'Show Hidden Devices' on the View menu at the top of the Device Manager window and see if more than one instance of this driver shows under that section.
Terry