Quoted from msj2222:Here is a place to register your machines and there serial #s, you can then print out a nice certificate which you can put away in a safe place, "just-in-case" http://www.ipsnd.net/Default.aspx
You can record the serial# here in Pinside under your collection details. There is a field for it. I fill out details from the sales on my games. Who I purchased from, price, condition, improvements, etc. Its a nice way to keep track of everything.
Hope you get your games back Rob! Just stay adament. The law should eventually be on your side especially since you have records and have done things in the correct manner.