I use melody assistant. You can try it for free, and when you are ready to buy it, it's only $20. It's very user friendly, and when you buy it, you can export your music as a wav, mp3, midi, or whatever, so you can create the music file and the sheet music at the same time. It has just about every instrument in the orchestra.

http://www.myriad-online.com/en/products/melody.htm