I solved my problem. I have 2.4 and 2.5 on my system that I use for writing code for other purposes and that I have not removed yet. I did have to change my path variable to indicate c:\PYthon26\arcgis10.0\.; (the semi-colon separates one value from the next in the path)and I have a PYTHONHOME variable that needed to be set to c:\Python26\arcgis10.0import arcpy works fine when IDLE appearsI may have to change my PYTHONHOME for other programs that use older versions of Python.