Reusable Preloader Using MovieClipLoader (Help)

Hi, I’m very new in flash and i make the “Reusable Preloader Using MovieClipLoader” tutorial in, the tut work just fine, this work creating a empty movie and making Jpgs appear on it trough a XML data… the only problem i got with it, is the Registration of the empty movie is in the Upper Left corner, and i think i need the Registration Mark in the center for display different sizes Jpgs, right? if so, please somebody can explain me how i could do it? i need center my pictures and they have different sizes.

Thanks, and sorry for my english.