Problem with instalation

Hi guys i have a problem with ionic instalation.

I instal ionic but it works only on path from user like this:

C:\Users\myUser\

When i eneter "ionic" i receive right information about ionic, but when i change directory for ex.
D:\myApp\ & enter the "ionic" fraze the cmd does not recognize command, can You help me with this?

P.S. npm & cordova working right in all folders on my computer