With the Windows upgrade, a new PC was necessary. One of my requiremnts this time was to mount the components directly to the cabinet, like a real arcade machine. Prior to this, I had a full tower case inside that was a real pain to work around.
Since there would be no case to install cards in, I went with an all-in-one motherboard by Epox and an AMD Athlon XP2000+ CPU. I ripped the drive cages and power supply out of the old case and screwed them directly to the wall of the cabinet. The 5.25" drive cage is mounted to the top of the coin vault, so the CD-ROM and floppy can be accessed through the coin door.
The picture below was taken during installation; the cables are all bound up and out of the way now.