Regshot is actually a very simple program, but nonetheless ingenious and incredibly useful. It is the best way to tell if a program is truly portable or not, and that is just one of it's many applications. But beyond comparing, it can also save the log to TXT files, for later use or later comparing. It defaults to the Temp directory, but you can also change the output folder to defaultly save in whatever folder you want.
But Regshot is not limited to just registry. You can also choose folders for Regshot to watch, and if any file is changed between shots (added/deleted/modified), it will appear in the report.
Speaking of which, the report is practically the main feature. You can either choose a simple TXT or an HTML file, which will list in a table all of the changes including their old and new values, additions, and deletions.
Perhaps the best part about Regshot is the lightness and swiftness about it. Even though some might think that it would take time to scan the entire registry and take a snapshot, but Regshot does it in a matter of seconds, and is packed in at only a required size of 75kb. It does, however, use quite the amount of RAM to snapshot; while idling, it sits aroun 300kb, but while shooting, it can peak at 60mb. It's also portable, however, meaning that you can take it anywhere, and open source to boot.
Regshot is an excellent hands-on tool for administrating your registry. It may not clean like other apps, but it lets you see crucial details that other registry cleaners mostly miss.