Download the HerlandWeatherGadget.zip file, rename it to HerlandWeatherGadget.gadget and doubble-click it to install on Vista or win7.
When asked for a site for realtime.txt, enter http://weather.herland.org/realtime.txt. (The suggested settings should be fine)
Update interval i secounds should be a positive number larger than 5.
For the Ubuntu screenlet, go to www.screenlets.org