My experience with Band-in-a-Box:
*sound of head bashing on keyboard followed by no sound*
Conversely, my experience with Fruityloops:
*sound of head bashing on keyboard followed by a few notes as a result, followed by actual music after further experimentation and tinkering with the tutorials*
What I would suggest if you did want to use this program, is to find some tutorials in whatever community is available for it. I'm not sure how popular it is now, but at the very least I remember it being mentioned in a couple of different music magazines back when I was heavily into that stuff (1994-1996ish)
Midi is balls-to-wall complex if it isn't set up properly - any number of variables and obstacles can cause your program to produce no sound whatsoever, not render properly to file, turn on your ceiling fan instead of playing a patch, etc. etc. It's incredibly flexible in an electronics kit sort of way; it can be used (and has been used) as a control interface for just about anything, including non-musical devices, since all sorts of information is packed into a "simple" midi signal, but if you make a small mistake like changing the channel an instrument is sending to, you can lose your signal entirely.
If you didn't want to bother with midi (and I wouldn't blame you, I only use when I have to, with my keyboard), or only wanted to tinker with it when you absolutely had to, I would suggest something like Fruityloops. It has a huge community with a lot of example tutorials and stuff you can hack apart shipped with it, plenty of flexibility, and you can generally make music with it out of the box after a bit of examination of how the process works. I would say that the samples and instruments provided aren't well-suited to most besides electronica and hip-hop stuff, but since you've already gotten BitB's sample library, that's a good starting point if you wanted to explore there.
The only problem is that it isn't exactly free. But I'd say that it (or something like it) is well worth it if you're seriously interested in making music, and not interested in a career in sound production (not a bad thing for sure!). You'll still learn quite a bit as you use it, but the interface (for me at least) isn't nearly as obtuse, and the learning curve is a lot nicer. I use Fruityloops for final production and tinkering with weird effects, and Powertab (free) for making more complex, melodic scores, as I'm much more used to tabulature notation versus standard.
Good luck!