There are numerous way to compare, modify, etc. two like files on Windows however using the application WinMerge will make things much easier. In the past I have opened the two files in Notepad or Notepad++, compared them, and then made the necessary changes. WinMerge is open source and created specifically for comparing similar files. There are so many benefits to using WinMerge including the ability to compare like folders (and their contents), save both files as projects, visually see location in files during the process, easily merge files, and many more. Below is a screenshot of what WinMerge looks like when comparing two PHP files.
I am fairly new to WinMerge however I am already seeing benefits of a powerful open source application. Currently WinMerge is installed on my Windows XP laptop and I have not noticed any issues.
WinMerge will allow you to easily merge files. In the viewing window you can copy changes right or copy them left. WinMerge will also visually highlight differences between the files so you can tell exactly what is different and needs to be merged together. The application will also log any changes made so you could revert the changes. If you backup the files as a project you could easily restore the files to previous revisions as well.
There are tons of options available when using WinMerge. Options run from very easy options to more complex options and so far all have been easy to configure. You can turn on or off line numbers to find your way around files. Colors and fonts can be modified to the most appealing look for you. Lines can be wrapped or not wrapped depending on what is going to be easiest for reading the file. White space can be highlighted or not as well as margins can be turned on or off.
The more I use WinMerge to compare or to merge files on Windows XP the more scenarios I find WinMerge useful for.