From the developer:
""FreeDiff is a free file difference viewer for Windows 95/98/ME - Windows 2000/NT/XP. Use it to analyze the changes between two revisions of a file. Note: FreeDiff is not an editor. The differences between files can be viewed but the files can not be modified. FreeDiff can be used to locate the differences in program source code files, HTML documents, and any other ASCII-based text files. A color-coded side-by-side display of the comparison results makes it easy to understand the differences between the two files at a glance. Other file types can also be compared if they are first saved in a text format. For example, MS Word documents and MS Excel spreadsheets can be saved in text format and compared. Two versions of the System Registry database can be exported from within RegEdit and then compared using FreeDiff.
""Features: Allows drag and drop of files onto FreeDiff for comparison; Auto-completes file specifications as they are typed in; Compares ASCII text files in a side-by-side format; Differences are shown with color highlighting; Differences down to the character-level are shown; Easy navigation from one difference to another; Search for text within the files; Bookmarks can be added to the comparison results; Ignore Space and Ignore Case comparison options supported; Files can be printed with the differences pointed out; Free of charge!""