I don't like unnecessary duplication. Is it possible to install python only once and have both ArcGIS and OSGeo4W use it?
This is how I did it for ArcGIS 9.3 and Osgeo4W with pythons 2.5 through 2.7:
You might need to add
It should be. Citing from ESRI system requirements:
Using ArcGIS 9.3.1, Python 2.5.4 is (officially) supported
I have an install of ArcGIS including Python 2.4 plus OSGeo4W w/ Python 2.5. Using 2.5 causes some problems with certain geoprocessing tools - unfortunately which tools don't work depends on the method used for creating the geoprocessing object itself.