Setting path 'C:\pik' in 'Environmental Variables'

To access the environment variables right click the My Computer icon then choose properties. Click 'Advanced system settings' link, click on 'Advanced' tab and then click 'Environment Variables'. In 'system variables, select 'Path' variable and click on Edit.
In the end of 'Variable Value'. add semicolon and C:\pik

;C:\pik

Click on Ok to save the settings.
In this way, you can set any variables path.