pics or vids downloaded to the SD card?
im guessing you mean on the phone? you put stuff from the computer onto your card and you want to view them? if you put them in the right folder they will appear in your gallery. if not you will need a app like astro that is a file management app and you can go through your phone and locate them that way.
no if i misunderstood you and you have pictures and videos on your phone and want to view them on the computer. simply plug your phone into your computer using a usb, and you will get a automatic pop up. click on open folder to view files. and locate your files.