Quoted from orangestorm87:
I wish somebody would setup a virtual machine or something with everything pre-configured and tables loaded. Then run that on your hardware and switch whatever due to your custom virtual pin.
(this coming from someone who does not own or has built a virtual pin)
There are legal reason behind this due to the simulator licenses and the copyrights on the tables. If you found someone who builds them or owns one, you may be able to get a copy of the hard drive from them, but they shouldn't be sold with them loaded.
As far as building your own, you can start with a smaller one. I'm making a tabletop one right now with a 24 inch playfield screen and a old 17 inch square monitor for the backbox. Get the software working, wire up some flipper buttons and start button to and old game pad and you got something to play. After that it's just making it bigger and adding force feedback and more input options.
Another idea for an easy first VPin is don't try to house the computer inside, just run a USB hub, Video and a audio cable out to your normal PC and use it as a "controller" with screens.
I wish there was a Virtual Pinball or Pinball Simulator section here on the forums, it would be nice to see some build threads.