Peter, you can do this:
1. Run Terminal.app, in Applications/Utilities
2. type 'sudo launchctl unload -w /System/Library/LaunchDaemons/com.apple.dashboard.advisory.fetch.plist' without the quotes, and press return.
3. Type your password and press return. When the command prompt returns it is done, it will return almost immediately with no feedback, which is its correct behaviour.
Launchctl interacts with the launchd process, which is responsible for running the advisory daemon. The "unload" tells launchd to stop launching the advisory daemon, and the "-w" tells launchd to rewrite the configuration to disable the daemon from launching permanently ( if you dont include the "-w" launchd will launch the advisory daemon at the next reboot ).
Later, if you decide you'd like to run it, do the same command in the terminal but use the word "load" instead of "unload". The "load" tells launchd to load the advisory daemon, and the "-w" tells launchd to rewrite the configuration to enable the daemon to launch again in the future, after the next reboot for example. The "-w" actually checks for a disabled status in the configuration and reverses whatever is currently in there. Disabled to enabled, and vica-versa.
