that will go in the machine
is is actually the easiest part.These specs were last updated July 2002.
Minimum Recommended Specs
TBBK's Recommended Specs
All I want to play is Pac-Man Specs
You can simply place the computer somewhere inside the arcade cabinet, or you can take it apart and install it where the original arcade gameboards were. You really only need the motherboard, power supply and hard drive, the rest of the computer can be saved for another project.
Select an operating system that you are familiar with. I use Windows 2000 in my personal MAME cabinet, but almost any OS will do. Linux and FreeBSD require a bit of configuration to skip having to log in. Do a fresh OS install and then install and configure MAME, and you will be ready to go.