Movie format changed when I wasn't looking

You experts may know. My newish TG5 is great. i have made plenty of movies and then downloaded onto my laptop or desktop. I can play them back in AVI. format. But today i made a short movie and it downloaded in MOV. format and my computer said it could not play that file. or there was something else wrong.

So I have tried to figure it out. Both computers play the old , 'saved' movies of dogs at the beach and such....but today the camera makes a movie , transfers it to laptop or desktop but neither computer will play the format which has changed to MOV. from AVI. i cannot find anything on the menu to change it back.

Any help

?????

P.S. i did download a piece of software that plays MOV. and it worked but very poor clarity of picture. Shocking actually.

thanks

Look forward to replies