Hey guys! I know for a fact that Jerry's computer is not a Mac. I have all of the episodes on tape and when this question arose, I started to examine the tapes. Reviewing the last 2 episodes I thought I saw something that might clear things up.
I had to make a video capture of a scene where you can clearly see the computer. Then I enhanced the image to zoom in on the PC, and guess what I saw?!!!! An "Intel Inside" logo on the lower right hand of the CPU!!!!
I guess this clears this thing up...