Some programs you can't do without; others are just nice to have. In the latter category, DiffExt is an ultrasimple utility that makes calling your favorite compare-file program a tad easier. The bare-bones configuration requires users to point to an appropriate executable. It then adds three extensions to the right-click context menu, each for a different method of comparison.
DiffExt doesn't actually compare the files; it merely sends the command to the program that does. The lack of a help file guarantees novices will be baffled, but they're not the target audience anyway. DiffExt is primarily for software developers who want to smooth every last inefficiency out of their workflow.
From Sergey Zorin:
Windows Explorer context menu extension to include commands for file comparison. With right click on a file or two files starts external file comparison utility. Diff-ext is a context menu extension that include commands for file comparison. Allow to save a file for later comparison (to allow comparison of files in different folders). Version 1.9.1 may include unspecified updates, enhancements, or bug fixes.