If it automatically moves the file to Others, it means that the phone does't recognize the file format.Are you sure that file is an mp3?Try with other files and see what happens...

Make sure the file is around 30 seconds long, make sure its wav or mp3 like(not sure if others can be played too), You can put it in any folder, but others is most prefered because no one uses it, and to find the others folder:
Main Menu -> File Manager -> press down 8 times [Other]
And if you really want, i can make a ringtone for you. Or for anyone.

after i read thru the sticky, you gotta limit the file size to 600kb on att ringtones. I'm personally getting software to do so right this second. Either change it to 30 seconds of music or lower sound quality so the kb per second changes the file size to less than 600 kb.

It should work in your phone after you put it in the 'others' folder does it not?

Hey I really need helping puttin the mp3 as a ringtone on mah SE W580i..i downloaded the drm n the sony ericsson pc suite..i did all the stuff needed fo the drm and then i tried puttin it into mah phone on the "phone mode" and then i put it into the folder where there are memory stick and the phone memory..but the problem is that how many people said it asks u where to put it or wat to do wid it..mah phone doesnt ask me tht..it just puts it in the "others" folder...and i really dont know wat to do now...i tried it many times...so plz it be really kind if u help me..THANX a lot