Take a look at the recent previous thread Music Annotation. There's been quite a bit of discussion about what's available.

Sibelius and Finale are the two "professional" programs most often cited, but they're both pretty expensive for the occasional user, and both of them are so loaded down with "features" that they can be a little daunting to learn. The last time I looked, Sibelius had a list price of about $700 US, but you can get it from a number of web sellers for about the same price they show for "academic" users - in the $300 range, as I recall.

There are quite a few reasonably good freeware/shareware programs. The thread linked above has links to a couple of places to look. You should be able to get an "adequate" notation program from commercial sources for $70 or less, and full/registered versions of some of the shareware programs are under $30 as I recall.

John