Can you connect your Garmin to a computer via USB or serial cable?
If USB, you can just copy+paste the track information out of its file system onto your computer, and upload directly to Google Earth.
If it's serial (and you don't have the appropriate cable), do a search online, there are a lot of smart people out there who are selling serial to usb cables for tasks just like this.
If it is some sort of serial cable and you do have the cable, you might be able to access the files on your Garmin and drag them onto your computer, and upload manually to Google Earth.
Also, if you can connect in any way to your computer, you might try the HomePort software, it may not need the unlock code like the old software did.