Sudoku Toolbox   
by The Tool Box Site   

Sudoku Toolbox is a sudoku solver, generator, editor, and teacher. Sudoku
Studio lets you solve an entire board, or just the next cell. It provides many
types of hints, including automated error checking, and showing all allowable
values. It teaches you how to better solve sudokus by providing the exact
reasoning to solve each step.
Sudoku Toolbox runs on Windows XP and needs the .Net Redistributable (the MSI Installer will automatically install this).
You can always check our free trial first to make sure that this program runs on
your machine.
Free Trial available at http://www.thetoolboxsite.com/SudokuDownload.aspx.