Download the PartWrite Self-Extracting ZIP Archive.
Prefer a ZIP Archive instead of a self-extracting executable? If so, click here.

The situation was made worse because it took a week for my assignments to be graded - by which time I had forgotten completely why I had written the music the way I had. In other words, I wish I had had instant feedback so I could understand and fix my erroneous ideas quickly.
This program provides a simple method for entering a small amount of music, usually around 4-6 measures (depending on the time signature and the size of your screen - unfortunately there is no scrolling implemented). You can enter your four voice part-writing exercise and the program will automatically check for parallel octaves and fifths, unequal fifths, hidden octaves and fifths, leaps by an augmented second, unresolved leading tones, and unresolved tritone leaps.
What it does *not* check for are doubling rules and missing chord tone rules. To some extent (especially for doubling rules), these rules arise out of the other part-writing rules above. In other words, you don't want to double the leading tone, because the leading tone needs go to the tonic, and if you do that you will be creating parallel octaves.
P.S.I ended up getting an 'A'.
Once you have extracted the contents of the ZIP file, you should have a single folder called "partwrite".
Before you run the program - Move the "Bach31.TTF" file into your fonts folder (inside the control panel).
Once the fonts are installed, double-click on "partwrite.exe" to execute the program. Once inside the program, be sure to browse the help file (under the help menu) to see how to use the program.
The partwrite program is written in Microsoft Foundation Classes, using Visual C++. I think the source code is fairly well written, meaning pretty clean. However, as always, it is provided as-is.
Note that partwrite uses the Bach Font for rendering music. More information on this font (it is a shareware font, although free for home users) can be found here.
I am, however, posting this software in the hopes that it will drive more traffic to my website. So, if you want to help me out, then please link to http://www.pnelsoncomposer.com. The link to the partwrite software can be found at: http://www.pnelsoncomposer.com/software/partwrite.
Thanks! Paul