MuseScore - Free Music Notation Software

http://musescore.org

Has a winPenPack version (i.e. no need to install) here... but it is not the latest version yet.

Quite easy to use and can use mouse, keyboard to enter the notes.

• Use number keys for the duration of the note
• Use corresponding letters for the pitches (with the <shift> key to enter chord note)

   C D Shift+F Shift+A E F

• <Ctrl> Up and Down to increase and decrease the pitch by octave
• ↑ (Up): Increase the pitch of a note by a semitone (uses sharps).
• ↓ (Down): Decrease the pitch of a note by a semitone (uses flats).
• R: Duplicate the last entered note
• Q: Halve the duration of the last entered note
• W: Double the duration of the last entered note
• Backspace: Undo last entered note
• X: Flip direction of note stem
• Shift+X: Move note head to opposite side of stem

For using the MIDI keyboard, make sure to connect and turn on the keyboard first before starting the software.

More info on note entry