Shoutbox

Each time I save a file, the extension isn't included.
Example: I make a file in photoshop, want to save it as PNG so I select PNG from the dropdown menu. I enter TEMP as the file name, but instead of saving it as TEMP.png, it saves it as TEMP. a plain file without extension. If I rename it manually to TEMP.png or during the saving procedure, name it TEMP.png, then the file is correct.

Same problem with audacity, meaning it's not photoshop related, I export a file as mp3, named it AUDIO, but it give an error about it not properly working since the extension is missing.

Does anyone know a solution to this?
Additional information:
Running XP Pro;
Never had this problem before;
Got 'tweaking' programs such as tune-up utilities (though these do not have options about extensions)

Thanks in advance.