You were told. What. To. Do.

Now, the problem is you were asked by RealPlayer to associate file types and you said, "YES".

Now you have to undo it.

Give yourself admin privileges.
Start Band in a Box.
Do what Matt said, again.
The icon view should now associate band in a box files with the software.

To be honest it's no big deal as long as band in a box know what the files are. Open it and try to load one.

I'm really thinking you have only a faint idea about this stuff right?

John Conley
Musica est vita