Well, it really depends on what type of phone you have.
Did your phone come with a cable, and software (like disk2phone for example) that lets you do that? If not, you can probably find one for cheap on ebay. Or, if not, does it have a memory card? Maybe you can get an adapter to plug in the memory card to your pc. Then you just transfer the file(s) to your memory card, then pop it back in the phone.
What kind of phone do you have, and what did it come with? I can probably give you more options then...
~Media Guru~
