I have received some attachments from a friend with the file extension .dat. Although My friend assures me that they are photographs, they open by default in notepad and in machine code only. How can I open these files and read them as photographs as they were sent?
The .dat file extension is used by Windows. If you have a folder of photos and then view them as thumbnails, Windows stores the thumbnails in a (hidden) .dat file. If your friend has sent you the entire contents of a folder, then that may include the .dat file. A friend of mine uploaded a folder of images to his website and then wondered where this extra .dat file had come from.
to change the file extension in xp, go to the tool tab in any folder - folder options - view - and uncheck the 'hide extensions for known filetypes' option. THEN right click on the file and rename it but you must remember to add an extension to it like .jpg .gif .exe etc but as gen2 says it is probably the thumbnail preview file