One of the tools that comes with the Windows 9X Resource Kit Sampler is Microsoft WinDiff, a file and folder comparison tool. Very handy for version checking and troubleshooting, this tool gives you a graphical display of the differences found between files and/or folders, on a line-by-line, color coded list.
WinDiff isn't installed as part of Windows 9X, but you can easily set it up yourself. Just insert your Windows CD and go to the '\tools\reskit\file' folder. Look for and copy WINDIFF.EXE, GUTILS.DLL, and WINDIFF.HLP to any folder, then create a shortcut to WINDIFF.EXE and drop it into your System Tools folder for easy access later.