persistent data in a program, and adding to it

So I'm building a stat-tracking program, and I'd like input on how to keep persistent data inside of a program. At the moment, I"m just opening a file each time the program opens (an "init" function inside of the main form_load), and before I end I then re-write-out that file. Of course, that means that I've got potential errors if that file is moved/doesn't exist/etc ... any other ways to do it? Once that's done, is there then a way to programmatically add to that persistent data? I'm thinking in terms of, if I have a pre-built array of information with an "init" function that populates it with data (the fibonacci numbers through 21, for instance), can I write code that expands that data set to the first 30 numbers only if a user requests?

thanks!!!!