Welcome to the Music and Sound forum on GD.net. Pull up a chair, listen to some tracks by your peers and discuss all things music and sound. We're happy to have you. Please check out the FAQ link for some basic (and mostly common sense) approaches used in this forum. If you have any questions, feel free to PM me.
If you have no real skill in music then you shouldn''t even attempt it.
However, if you know music, I suggest using Musicshop by Opcode. I''m not sure if there is a PC version, but it is without a doubt the best composing software there is. It''s cheap too ($100). No other program gets you going quicker.