Tool Validator edit - How to change what editor is used ?

Hi

When editing a tool validator class I do as described in the help:

" ... to program a ToolValidator class, right-click your tool, click Properties, click the Validation tab, then click Edit. This opens your installed Python editor, such as IDLE or PythonWin. ... "

taken from: http://help.arcgis.com/en/arcgisdesk...000w000000.htm

Only on my computer the pyton code opens in Notepad, not in IDLE nor PyWin ... ?

QUESTION: Where do I change the setting that controls which editor is used?

I run ArcGIS 10.1 on a win7
In the windows environment .py files are set to default open with .../python.exe

Best Regards
Martin Hvidberg