Photo captioning

I find cnet to be of great help in not only learning new tricks and downloading useful programs, but now your different forums providing tremendous opportunities - thank you!

I need a simple free photo captioning program, so that many photos may contain the titles or names etc which could be used for slide shows etc. If possible, if it could be reversible or editable to avoid having to keep originals separately. Recently, I downloaded FxFoto, which I have found to be very useful, but irreversible. Would appreciate feedback of other similar free and easy programs.