This is the info for getting WL to upload to WU.http://wiki.wunderground.com/index.php/PWS_-_WeatherLink
It has a .dll that you need to add.
TO INSTALL THE MODULE
1) First install WeatherLink 5.5.1 (or later) or upgrade an earlier version.
If you do not already have WeatherLink version 5.5.1, you can upgrade from versions 5.0 - 5.4, goto: Davis Software Support
2) Download the expansion module here. Save the WuiWlink_1.dll file to your Weather Link Expansion Modules directory:
The Expansion Modules directory is usually in "C:\WeatherLink\Expansion_Modules".
That is... the file needs to go into a directory named "Expansion_Modules" within the Weather Link installation directory. You may have create the "Expansion_Modules" directory if it isn't already there.
3) Quit and restart (or start) the WeatherLink application.
4) Goto the "File" menu and select "Manage Modules".
5) Click the "Add Module" button. Find and select the WuiWlink_1.dll file.
6) Click "okay" several times until all of the dialog windows close.
7) Restart WeatherLink.
TO SETUP THE MODULE
1) Select "Wunderground Settings" from the "File" menu.
2) Enter your weather station ID and password, and the frequency of updates. You can find your Weather Station ID from: My Stations. Your password is the password you use to login to the wunderground.com site.
3) If you wish, click the "Test" button, and an observation will be sent. A dialog will appear indicating whether the operation was successful.
That's it. If your station is connected, it should start uploading observations using the new module.
If you want to run multiple programs, you need VirtualVP. http://www.softwx.com/downloads.html
That depends on the version of the data logger. Others can chime in.