Okay, here’s the scoop.
If you’ve come to love Delorme’s mapping software and their GPS receiver (LT-20 or LT-40) and you’re using their serial emulator with Windows XP to send the signal to StormLab, you’re going to be disappointed when you attempt to use the same setup with Windows 
7, 64 bit technology. Bottom line, it does not work and you won’t get any sympathy from Delorme either. They’re not supporting 64 bit and have no plans to do so.
So, here’s what you do. Don’t use their puck. If you have one, throw it in the trash. Now, don’t get all teary-eyed on me. You can still use “Street Atlas”, but you’ll need to spend a little more money on a new GPS receiver. Throw away a 
perfectly good GPS antenna? It goes against my grain as well. But, believe me when I say this, save yourself a ton of aggravation and just toss it.
I’m using my Garmin hand-held GPSMAP 60CSx. It works great with the Delorme mapping software and Windows 7, 64 bit. I also installed GPSGate software (39.95) to send the signal to both StormLab and Spotter Network. I know, the Garmin GPSMAP is tad pricey, costing about $400.00 (SRP) plus the cost of the maps you want. A less expensive option is the Globalsat, BU-353 USB receiver, it’ll work too. The Globalsat is a lot more affordable at less than 40 bucks through Amazon.com.
That’s the work-around.
Good luck.