I came accross an issue today, when i installed ionic and cordova for a test project. i did this
npm install -g cordova ionic
ionic start myapp tabs
ENV: WINDOWS7, NODE.JS, IONIC, CORDOVA
I solved my problem (stated above) by upgrading node.js and reinstalling ionic package after removing it.
Second i also found out that to specify path to app location, below command will work.
ionic start [absolute-path-to-app-folder] [template-optional]
ionic start c:\myApp will create a blank app in C drive
Hope this can help someone. i spent a week digging this out.