DirDiff

DirDiff is a compact and portable piece of software that lets you compare files from two directories, in order to spot differences. It can be seamlessly figured out, even by users with little or no experience in such tools.
Since installation is not a prerequisite, you can simply drop the executable file to any location on the hard drive and run it.
Alternatively, you can save DirDiff to a USB flash drive or similar storage unit, in order to run it on any computer with minimum effort.
What's more important is that the Windows Registry section does not get entry updates, and files do not remain on the hard drive after program removal.
The interface of the application is plain and extremely simple to work with. You can load two directories into the workspace using either the file browser or "drag and drop" function. It is also possible to compare the content of two files of any format.
Each directory is assigned with a particular color (red, green), in order to highlight files which belong only to that particular location. Identical files are not shown in highlights.
You can make the program ignore dates and specific files or folders, copy file paths to the Clipboard, use a search function to the next or previous difference when dealing with large amounts of files, as well as update the list.
DirDiff is very low-demanding when it comes to the CPU and system memory, has a good response time and works smoothly. We haven't come across any issues throughout our evaluation, since the app did not hang, crash or pop up error dialogs. On the downside, DirDiff has not been updated for a while.