I'm on Windows Vista. I've been using IDLE, the default Python IDE ever since installing Python.
I long enjoyed the functionality of right-clicking a .py file and selecting "Open with IDLE" until one day, this was gone. The .py association seems to have been lost at that same time, as double-clicking a .py file will now open it in Notepad by default, and the thumbnail changed from the Python thumbnail to some unrecognizable default looking one.
Hitting F5 on an unsaved window of IDLE used to prompt me to save it, and then it would run it. Now, the prompt is skipped and it the "Open" dialog appears. Open!
I am positive that I've never touched IDLE's settings. What is going on?