A computer-assisted imaging and localization system assists the physician in positioning implants and instruments into a patient's body. The system displays overlapping images—one image of the surgical site with the patient's anatomy and another image showing the implant(s) or instrument(s). The overlapping image of the implant/instrument is moved over the static image of the anatomy as the implant/instrument is moved. These moving image of the implant/instrument can be an unaltered image or an image altered to intensify or mitigate the anatomical or non-anatomical aspects of the moving image. Sliding these images over one another helps the surgeon in positioning devices or instruments with a high degree of accuracy and with a limited number of additional x-rays.