No module named arcpy for ArcGIS 10.0

Traceback (most recent call last): File "D:\python\croplink\interfacetest.py", line 5, in import arcpy ImportError: No module named arcpy

In my system python 26 is installed for arcgis10.0 and python 27 is also installed and working properly. I can import arcpy from ArcGIS python window but, the failed the other way. I already tried setting path variables