I have a question which is kind of annoying, but I am going to ask it anyway .

I'm looking for a database sysem to use in my software which does not have to be pre-installed on the enduser his computer.

What i'm basicly looking for is a lightweight thing, (just a couple of MBytes), which is relational and supports the simple SQL queries.

I can't think of anything really suitable: SQLServer, MySQL, Oracle, Access, XML, ...

Is there a clear solution? I can imagine this sounds like the Coke-Zero commercials: "What about great life without downsides?" But fact is that there are a lot of existing applications that use an SQL supporting database which don't require a preinstalled database system.

... and hopefully it's free

Thank you in advance, I'm really curious.