Maven http plugin error on Windows

I did a quick search for this problem when I first had it and couldn't find anything about it, so here's a solution.

Building a new project with Maven 3.0.3 on Windows, if you get an error like the following:

[ERROR] No plugin found for prefix 'http' in the current project and in the plugin groups [org.apache.maven.plugins, org.codehaus.mojo] available from the repositories ...

...first confirm that you're using the default Windows shell. Using an atypical shell caused the above problem for me, likely due to different handling of environment variables. You don't have to change your shell: just launch the default shell with "cmd.exe" and run the command from within there.