I've been going through a similar problem. For Christmas I got a Magellan Sportrak Color GPS and tried to hook it up to my laptop. The Magellan comes with a really silly cable that has a serial connector. Hello! This is 2005, who still uses serial? My laptop has only USB. I bought a Radio Shack adapter cable and managed to get it sort of working if I booted the PC first with only the adapter attached and plugged in the GPS once the Streets and Trips software was running. Otherwise, the PC crashed and rebooted.
I figured, who needs this hassle so I am selling the Magellan on eBay.
Then I bought Delorme Earthmate and Street Atlas software. Works like a dream and I love the voice directions but the software interface is not as smooth as Microsoft Streets and Trips and Street Atlas doesn't include any detail maps of Canada whereas Streets and Trips does. (Excuse me for saying something nice about Microsoft.
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Then I tried to use Streets and Trips with the Delorme Earthmate. S&T wouldn't recognize the Earthmate GPS. I had installed the driver. Had to go through a bunch of hoops to get it seen by the laptop and once it was it seems to interfere with my mouse!
They say that the definition of insanity is when you do the same thing over and over again expecting different results.... Well, I'm thinking of getting the Microsoft Streets and Trips GPS now.....
Oh well...