If you want a traditional score editor, I'd suggest Finale Notepad. Yo need to register to download it, but registration and the program itself are free. The newest version now reads and exports MIDI files - a really useful addition. If you want a recorder and mixer, you could try Reaper. It's non-expiring shareware and is very good.

I use both; I compose in Finale then import the MIDIs to do the instrumentation and mixing in Reaper.

Finale Notepad - http://www.finalemusic.com/notepad/
Reaper - http://reaper.fm/