Today I installed Node.js on a new Windows 8.1 machine. I downloaded the latest version from nodejs.org and tried to use npm. I got the following exception:
Error: ENOENT, stat 'C:\Users\Username\AppData\Roamin\npm'
The solution is very simple: Just create the folder: C:\Users\Username\AppData\Roamin\npm Afterwards node (and npm) works as expected.
This behavior is a bug in the recent version of the node installer (see here for more details).