Is there a way to change the "file extension" of a file?

Yes. Right click on the file and go to "Rename." If you can't see the extension, go to "Tools", "Folder Options", "View" tab and uncheck "Hide extensions for known file types."

Change Type Of File

Yes, you can change the file extension of a file. As JJ said you can right click on the file and go to "Rename." If you can't see the extension, go to "Tools", "Folder Options", "View" tab and uncheck "Hide extensions for known file types." However, just renaming the file won't necessarily convert the file to the new type. If you have a text file named whatever.txt, for example, you can rename it to whtever.pdf, but don't expect to be able to open it with Adobe Reader. If you just want to change the case of the extension, it should have no effect.

Sounds like the permissions have been set to not allow showing hidden files and folders. Log in as administrator and you should be able to change it. Good Luck

Extensions aren't case specific. .mp4= .MP4

Maybe you need a codec to play .mp4 files?

Go to TOOLS, FOLDER OPTIONS.. click the VIEW tab, and uncheck HIDE EXTENSIONS TI KNOWN FILE TYPES.. and then you will be able to see the file extension and re name them accordingly.

no, you can't just change an ext.

there is lots of software that will convert files for you,

say like an AVI to DVIX or mp4 to ..... and so on

but for your i.e. their all ready the same

NO JJ you can just change them!!!!