Brad,

You are going to have to hack open the file to see what the structure looks like and see if it has a DBF type header or not. It could be any of a number of plug in databases that are available for Delphi. I know of about 6 that are commonly used. The extension does not always give it away. However, IDX is a common extension for XBASE type index files. There are database drivers from Sequiter CodeBase, Advantage Database, Apollo Systems, Borland, etc. It could also be home grown.