DrinkCompare is a free program which allows you to compare two or more files each other, or files from two entire directories including all their subdirectories. It's intended for people who make CDs or backup copies and want to test the correctness of a copy in comparison with original. It can also be used to test the correct working of a media, by comparing a directory with itself.
The comparison is done reading entirely the contents of all files, and the response for every couple of files can be: "equal", "different contents", "not found in 2nd directory", "1st file appears truncated", "2nd file appears truncated". It's also possible to choose a fast comparison mode in which only files sizes are compared, and in that case response will be only "equal (maybe...)" or "different size".
Program interface is simple and friendly, all buttons provide hints when mouse comes over them, and some yellow-highlighted labels indicate steps to do or the actual status of an operation. Comparison results are shown in a report window where text can be printed, saved (in text format or HTML with appropriate formattation) or viewed in HTML format on the fly.
A set of additional options, all in the main window, some of which visible or not according to the context, allows you to execute comparisons with extreme flexibility.