Fred,
If you like using Delorme products (such as Street Atlas), you could simply upgrade your OS to Windows 7 (or purchase a new laptop), call Delorme to purchase a BT-20 puck, and you would be on your way to chasing the way you are accustomed to. I would definitely recommend going the Bluetooth route as it cuts one more cable out of the way. I have Windows 7 Professional 64 bit and use it in conjunction with Street Atlas 2010 Plus, the BT-20 puck, and GPSGate to share the signal amongst several applications such as Spotter Network, GRL3, GRAE, and Street Atlas. You could also consider one of the Globalsat pucks that utilize Bluetooth as I've been thinking on getting one of those myself. Wes Carter also linked me to Amazon where they sell the BT-20 puck bundled with the Street Atlas software for a nominal price.
The LT-40 just wont work, it's that simple. Globalsat also makes a USB puck that a lot of chasers here use. They are very reliable and work well for most applications. If you have any other questions just let us know.
Thanks,
Mark