stefan, I don't know what software you will end up using, but I like you do some "for fun" composing with keyboard, and I use all-freeware/shareware software. For a recording software, I use a program called "DDClip Pro" that works rather well for its class. It is not nearly as professional as something like Acid or Protools, but it is far less expensive.

A good drum machine is a program called "leafdrums". I don't know the URL for it, but google should find it. It is shareware, but there is no restriction on anything. It comes with a standard drum set but you can use whatever wav sounds you record as "drums", and it has up to 64th beat resolution. Not bad for free software! The interface is a little confusing at start but you get used to it.

Hope this might help, and good luck with your composing career!

Jonathan