Just found this through Google from:
http://usmle.egmedicine.com/2008/01/11/step-3-to-include-media-clips-starting-in-march-2008/
"A small number of multiple-choice items with associated audio and/or video clips will be introduced into the USMLE Step 3 Examination beginning in early March 2008. No more than 5 items with associated media clips will appear in a single examination. The 2008 USMLE Orientation Materials include a small number of multiple-choice items that contain exhibits involving audio and/or video clips. Instructions for practicing with items with associated media clips on Step 1, Step 2 CK, and Step 3 are provided in the Tutorials for each Step examination in the orientation materials.
Items with associated media were introduced into Step 2 CK in 2007, and will be introduced into Step 1 later in 2008. An announcement will be posted to the USMLE website approximately 2 months before any items with associated media clips appear on Step 1 examinations. Additional information will be posted to the USMLE website as it becomes available."