Schoening
If you add the -g (= global) flag to the install command (npm install socket.io -g), that should ensure that it'll be on a filepath where the node command can locate it. (My PATH environment includes: C:\Program Files\nodejs\;)
[ADDED]
For reference:
My node.exe is in
C:\Program Files\nodejs
My socket.io files are in
C:\Program Files\nodejs\node_modules\socket.io
My server development files are in:
C:\Program Files\nodejs\dev\c2mp
When I installed
Executing 'node server.js' in C:\Program Files\nodejs\dev\c2mp\ transparently accesses all necessary files/modules (including of course socket.io).