Really quick one today but it may help someone out. A friend recently sent me a jpeg she couldn’t open on her PC. I went to my free graphics editor IrfanView and tried to open it. It prompted Warning! The file xxx.jpg is a TIF file with incorrect extension! Rename? Once it had renamed it with the tif extension, there was no problem opening it and then saving as a jpeg. I learned today on Twitter (@WollemiPine) that this also works if a jpeg is really a bmp file with the wrong extension.
So if you’re having problems opening a jpeg or indeed another graphics file format, and you haven’t tried IrfanView, download it and see if in fact it’s been saved with the wrong extension. It won’t always work – you may not be able to open your jpeg because of a corrupt header for example.