When to use a database...

Hello everyone,
This is my first post on this forum. I appreciate any help you can give me in advance.
I recently decided that I wanted to get back the programming skills I used to have in college. (My job for the past five years hasn't involved any software development.) So, in leu of this, I decided to make a piece of software that would be helpful to myself and my friends. At the same time, I figured I could learn about programming.
The application I'm trying to write is designed to help me build character sheets in the role-playing game system that I use. I don't plan to sell this application unless that company wishes to buy it from me. Anyway, this program will need to access a set of data in the form of hundreds (definitely not thousands) of skills, hundreds of pieces of equipment (probably not thousands), tens of advantages/disadvantages, etc.
So, I was thinking... Perhaps the best way to design this is to have my application connect to a back-end database. The problem with this is that I am not aware of any free databases that I could include in my application and sell to the company that produces the gaming system. So... now I'm thinking that I should simply store the data in XML files and load ALL of it into class variables when the program is started.
Thoughts? How many pieces of data make a database absolutely necessary?
Thanks again,
Lemmywinks

Perseios,
Thanks for the reply. It was really helpful. Good point about the use of a database for complex queries. When it comes down to it, I can restrict the user to search for skills, equipment, etc using a single search, but I think the application would be MUCH more powerful with a backend database. Plus, I'll get to learn a lot.
I have a couple questions for you, however. I hope you don't mind answering them.
(1) Is the hypersonic DB free to be distributed with a for-profit program? I.e. If I end up selling this application to the company that makes this role-playing game, can they sell it to customers?
(2) My basic concept was to have a class called "character" which contained a number of descriptive variables and methods, as well as classes called "skill", "advantage", "disadvantage", "equipment", etc. The more I think about it, however, it more I think that if I'm storing all these entities into a database, do I really need to read them in as class objects? I could still store the methods in these classes, but I wouldn't have to store data there. Thoughts? Basically this application will allow someone to build a character and then save it to the database. Users could have a database of characters, skills, ads, disads, equipment, etc, etc.
Thanks for your help,
Lemmywinks

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Edited by: Alvaro Tejada Galindo on Feb 12, 2008 12:45 PM

Thank you Thomas,
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waiting...
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