If they are 1980's Bally, Gottlieb or MrGame tables, you'll need to go to
www.vpforums.org and download the special Bally, GT3 and MrGame NVRAM files. Look under Essential Files at the top of the page. Unzip these to the vpinmame\nvram folder. When asked if you want to replace any of the files in the folder, click Yes.