Installing nodepacks on Windows fails

[steve2507]

C:\Users\...>xiblepm nodepack install math
{ Error: spawn npm ENOENT
    at exports._errnoException (util.js:1050:11)
    at Process.ChildProcess._handle.onexit (internal/child_process.js:193:32)
    at onErrorNT (internal/child_process.js:367:16)
    at _combinedTickCallback (internal/process/next_tick.js:80:11)
    at process._tickCallback (internal/process/next_tick.js:104:9)
  code: 'ENOENT',
  errno: 'ENOENT',
  syscall: 'spawn npm',
  path: 'npm',
  spawnargs:
   [ 'install',
     'https://registry.npmjs.org/xible-nodepack-math/-/xible-nodepack-math-0.1.0.tgz' ] }

C:\Users\...>node --version
v7.10.0

C:\Users\...>npm --version
4.2.0

The same error is raised when installing a nodepack from the editor.