You don't need a 78 rpm turntable for the 78s, if you're using Cool Edit Pro(or its successor, Audition 1.5.) Just play the 78 in at 33, then use the Pitch Control to speed it up. The setting would be 78/33, or 236%. Or play it in at 45, and speed it up 173%. Make sure you select the option that preserves neither time nor pitch.

Along the same lines, I've copied cassettes in at double speed, then halved the time with the control. It cuts the real time involvement in half.