In order to scan any type of films (negative or transparency), the
scanner requires a back lighting source which goes through the film so
that the scanner sensor can "see" the image on the film. Usually this
backlight is built into the scanner top, if it exists, and when it is
turned on through software, the lower scanner lamp turns off. The
"normal" scanner light illuminates from the bottom to light reflective,
rather than transmissive images sources, like paper and prints.
Some people use reflective print scanners with slides and negs but the
result is quite inferior and requires a lot of manipulation to get
anything approaching useful.
Also, if you wish to scan things like 35mm slides or negs, besides
needing the backlighting top you will require both a high resolution
optical scanning ability (at least 1000 ppi) and software for inverting
the color and removing the orange cast found in negative color film.
Art
If you are interested in issues surrounding e-waste,
I invite you to enter the discussion at my blog:
http://e-trashtalk.spaces.live.com/